There's obviously something wrong with your config table, as another mandatory row is missing: login_threshold.
Please execute the following query with phpMyAdmin:
INSERT INTO cpg15x_config VALUES ('admin_activation', '0');
INSERT INTO cpg15x_config VALUES ('alb_desc_thumb', '1');
INSERT INTO cpg15x_config VALUES ('alb_list_thumb_size', '50');
INSERT INTO cpg15x_config VALUES ('album_list_cols', '2');
INSERT INTO cpg15x_config VALUES ('album_sort_order', 'pa');
INSERT INTO cpg15x_config VALUES ('albums_per_page', '12');
INSERT INTO cpg15x_config VALUES ('allow_duplicate_emails_addr', '0');
INSERT INTO cpg15x_config VALUES ('allow_guests_enter_file_details', '0');
INSERT INTO cpg15x_config VALUES ('allowed_doc_types', 'doc/txt/rtf/pdf/xls/pps/ppt/zip/gz/mdb');
INSERT INTO cpg15x_config VALUES ('allowed_img_types', 'jpeg/jpg/png/gif');
INSERT INTO cpg15x_config VALUES ('allowed_mov_types', 'asf/asx/mpg/mpeg/wmv/swf/avi/mov');
INSERT INTO cpg15x_config VALUES ('allowed_snd_types', 'mp3/midi/mid/wma/wav/ogg');
INSERT INTO cpg15x_config VALUES ('allow_email_change', '0');
INSERT INTO cpg15x_config VALUES ('allow_memberlist', '0');
INSERT INTO cpg15x_config VALUES ('allow_private_albums', '1');
INSERT INTO cpg15x_config VALUES ('allow_unlogged_access', '3');
INSERT INTO cpg15x_config VALUES ('allow_user_account_delete', '0');
INSERT INTO cpg15x_config VALUES ('allow_user_album_keyword', '0');
INSERT INTO cpg15x_config VALUES ('allow_user_edit_after_cat_close', '0');
INSERT INTO cpg15x_config VALUES ('allow_user_move_album', '0');
INSERT INTO cpg15x_config VALUES ('allow_user_registration', '0');
INSERT INTO cpg15x_config VALUES ('allow_user_upload_choice', '1');
INSERT INTO cpg15x_config VALUES ('auto_resize', '1');
INSERT INTO cpg15x_config VALUES ('batch_proc_limit', '2');
INSERT INTO cpg15x_config VALUES ('bridge_enable', '0');
INSERT INTO cpg15x_config VALUES ('browse_batch_add', '1');
INSERT INTO cpg15x_config VALUES ('browse_by_date', '0');
INSERT INTO cpg15x_config VALUES ('caption_in_thumbview', '1');
INSERT INTO cpg15x_config VALUES ('categories_alpha_sort', '0');
INSERT INTO cpg15x_config VALUES ('charset', 'utf-8');
INSERT INTO cpg15x_config VALUES ('clickable_keyword_search', '1');
INSERT INTO cpg15x_config VALUES ('comment_akismet_api_key', '');
INSERT INTO cpg15x_config VALUES ('comment_akismet_counter', '0');
INSERT INTO cpg15x_config VALUES ('comment_akismet_enable', '0');
INSERT INTO cpg15x_config VALUES ('comment_akismet_group', '0');
INSERT INTO cpg15x_config VALUES ('comment_approval', '0');
INSERT INTO cpg15x_config VALUES ('comment_captcha', '1');
#INSERT INTO cpg15x_config VALUES ('comment_email_notification', '0');
INSERT INTO cpg15x_config VALUES ('comment_placeholder', '1');
INSERT INTO cpg15x_config VALUES ('comment_promote_registration', '0');
INSERT INTO cpg15x_config VALUES ('comments_anon_pfx', 'Guest_');
INSERT INTO cpg15x_config VALUES ('comments_per_page', '20');
INSERT INTO cpg15x_config VALUES ('comments_sort_descending', '0');
INSERT INTO cpg15x_config VALUES ('comment_user_edit', '1');
INSERT INTO cpg15x_config VALUES ('contact_form_guest_email_field', '2');
INSERT INTO cpg15x_config VALUES ('contact_form_guest_enable', '0');
INSERT INTO cpg15x_config VALUES ('contact_form_guest_name_field', '2');
INSERT INTO cpg15x_config VALUES ('contact_form_registered_enable', '1');
INSERT INTO cpg15x_config VALUES ('contact_form_sender_email', '1');
INSERT INTO cpg15x_config VALUES ('contact_form_subject_content', 'Coppermine gallery contact form');
INSERT INTO cpg15x_config VALUES ('contact_form_subject_field', '0');
INSERT INTO cpg15x_config VALUES ('cookie_name', 'cpg15x');
INSERT INTO cpg15x_config VALUES ('cookie_path', '/');
INSERT INTO cpg15x_config VALUES ('cookies_need_consent', '0');
INSERT INTO cpg15x_config VALUES ('count_admin_hits', '0');
INSERT INTO cpg15x_config VALUES ('count_album_hits', '1');
INSERT INTO cpg15x_config VALUES ('count_file_hits', '1');
INSERT INTO cpg15x_config VALUES ('custom_footer_path', '');
INSERT INTO cpg15x_config VALUES ('custom_header_path', '');
INSERT INTO cpg15x_config VALUES ('custom_lnk_name', '');
INSERT INTO cpg15x_config VALUES ('custom_lnk_url', '');
INSERT INTO cpg15x_config VALUES ('custom_sortorder_thumbs', '1');
INSERT INTO cpg15x_config VALUES ('debug_mode', '0');
INSERT INTO cpg15x_config VALUES ('debug_notice', '0');
INSERT INTO cpg15x_config VALUES ('default_dir_mode', '0755');
INSERT INTO cpg15x_config VALUES ('default_file_mode', '0644');
INSERT INTO cpg15x_config VALUES ('default_sort_order', 'na');
INSERT INTO cpg15x_config VALUES ('disable_comment_flood_protect', '0');
# INSERT INTO cpg15x_config VALUES ('display_admin_uploader','0');
INSERT INTO cpg15x_config VALUES ('display_comment_approval_only', '0');
INSERT INTO cpg15x_config VALUES ('display_comment_count', '0');
INSERT INTO cpg15x_config VALUES ('display_coppermine_news', '1');
INSERT INTO cpg15x_config VALUES ('display_filename','0');
INSERT INTO cpg15x_config VALUES ('display_film_strip', '1');
INSERT INTO cpg15x_config VALUES ('display_pic_info', '0');
INSERT INTO cpg15x_config VALUES ('display_redirection_page', '0');
INSERT INTO cpg15x_config VALUES ('display_reset_boxes_in_config', '0');
INSERT INTO cpg15x_config VALUES ('display_sidebar_guest', '1');
INSERT INTO cpg15x_config VALUES ('display_sidebar_user', '1');
INSERT INTO cpg15x_config VALUES ('display_stats_on_index', '1');
INSERT INTO cpg15x_config VALUES ('display_thumbnail_rating', '0');
INSERT INTO cpg15x_config VALUES ('display_thumbs_batch_add', '1');
INSERT INTO cpg15x_config VALUES ('display_uploader', '0');
INSERT INTO cpg15x_config VALUES ('display_xp_publish_link', '0');
INSERT INTO cpg15x_config VALUES ('ecard_flash', '0');
INSERT INTO cpg15x_config VALUES ('ecards_more_pic_target', 'http://yoursite.tld/your_coppermine_folder/');
INSERT INTO cpg15x_config VALUES ('editpics_ignore_newer_than', '0');
INSERT INTO cpg15x_config VALUES ('email_comment_notification', '0');
INSERT INTO cpg15x_config VALUES ('enable_encrypted_passwords', '1'); # Do not remove - this record IS needed to make sure that there is no double-encryption when updating
INSERT INTO cpg15x_config VALUES ('enable_help', '1');
INSERT INTO cpg15x_config VALUES ('enable_menu_icons', '2');
INSERT INTO cpg15x_config VALUES ('enable_plugins', '1');
INSERT INTO cpg15x_config VALUES ('enable_smilies', '1');
INSERT INTO cpg15x_config VALUES ('enable_thumb_watermark', '1');
INSERT INTO cpg15x_config VALUES ('enable_unsharp', '0');
INSERT INTO cpg15x_config VALUES ('enable_watermark', '0');
INSERT INTO cpg15x_config VALUES ('enable_zipdownload', '0');
INSERT INTO cpg15x_config VALUES ('filter_bad_words', '0');
INSERT INTO cpg15x_config VALUES ('first_level', '1');
INSERT INTO cpg15x_config VALUES ('forbiden_fname_char', '$/\\\\:*?"'<>|` &#@');
INSERT INTO cpg15x_config VALUES ('fullpath', 'albums/');
INSERT INTO cpg15x_config VALUES ('fullsize_padding_x', '5');
INSERT INTO cpg15x_config VALUES ('fullsize_padding_y', '3');
INSERT INTO cpg15x_config VALUES ('gallery_admin_email', 'you@somewhere.com');
INSERT INTO cpg15x_config VALUES ('gallery_description', 'Your gallery description here');
INSERT INTO cpg15x_config VALUES ('gallery_name', 'Your gallery name here');
INSERT INTO cpg15x_config VALUES ('global_registration_pw', '');
INSERT INTO cpg15x_config VALUES ('guest_token_cleanup', '0');
INSERT INTO cpg15x_config VALUES ('hit_details', '0');
INSERT INTO cpg15x_config VALUES ('home_target', 'index.php');
INSERT INTO cpg15x_config VALUES ('im_options', '-antialias');
INSERT INTO cpg15x_config VALUES ('impath', '/usr/bin/');
INSERT INTO cpg15x_config VALUES ('jpeg_qual', '80');
INSERT INTO cpg15x_config VALUES ('keep_votes_time', '30');
INSERT INTO cpg15x_config VALUES ('keyword_separator', ';');
INSERT INTO cpg15x_config VALUES ('lang', 'english');
INSERT INTO cpg15x_config VALUES ('language_autodetect', '1');
INSERT INTO cpg15x_config VALUES ('link_pic_count', '1');
INSERT INTO cpg15x_config VALUES ('link_last_upload', '0');
INSERT INTO cpg15x_config VALUES ('log_ecards', '0');
INSERT INTO cpg15x_config VALUES ('login_expiry', '10');
INSERT INTO cpg15x_config VALUES ('login_method', 'username');
INSERT INTO cpg15x_config VALUES ('login_threshold', '5');
INSERT INTO cpg15x_config VALUES ('log_mode', '0');
INSERT INTO cpg15x_config VALUES ('main_page_layout', 'breadcrumb/catlist/alblist/random,2/lastup,2');
INSERT INTO cpg15x_config VALUES ('main_table_width', '100%');
INSERT INTO cpg15x_config VALUES ('make_intermediate', '1');
INSERT INTO cpg15x_config VALUES ('max_com_lines', '10');
INSERT INTO cpg15x_config VALUES ('max_com_size', '512');
INSERT INTO cpg15x_config VALUES ('max_com_wlength', '38');
INSERT INTO cpg15x_config VALUES ('max_film_strip_items', '5');
INSERT INTO cpg15x_config VALUES ('max_img_desc_length', '512');
INSERT INTO cpg15x_config VALUES ('max_tabs', '12');
INSERT INTO cpg15x_config VALUES ('max_upl_size', '1024');
INSERT INTO cpg15x_config VALUES ('max_upl_width_height', '2048');
INSERT INTO cpg15x_config VALUES ('media_autostart', '1');
INSERT INTO cpg15x_config VALUES ('min_votes_for_rating', '1');
INSERT INTO cpg15x_config VALUES ('normal_pfx', 'normal_');
INSERT INTO cpg15x_config VALUES ('offline', '0');
INSERT INTO cpg15x_config VALUES ('old_style_rating', '0');
INSERT INTO cpg15x_config VALUES ('orig_pfx', 'orig_');
INSERT INTO cpg15x_config VALUES ('performance_page_generation_time', '0');
INSERT INTO cpg15x_config VALUES ('performance_page_query_count', '0');
INSERT INTO cpg15x_config VALUES ('performance_page_query_time', '0');
INSERT INTO cpg15x_config VALUES ('performance_timestamp', '0');
INSERT INTO cpg15x_config VALUES ('personal_album_on_registration', '0');
INSERT INTO cpg15x_config VALUES ('picinfo_movie_download_link', '1');
INSERT INTO cpg15x_config VALUES ('picture_table_width', '100%');
INSERT INTO cpg15x_config VALUES ('picture_use', 'thumb');
INSERT INTO cpg15x_config VALUES ('picture_width', '400');
INSERT INTO cpg15x_config VALUES ('purge_expired_bans', '1');
# INSERT INTO cpg15x_config VALUES ('randpos_interval', '1063623637');
INSERT INTO cpg15x_config VALUES ('rate_own_files', '0');
INSERT INTO cpg15x_config VALUES ('rating_stars_amount', '5');
INSERT INTO cpg15x_config VALUES ('read_exif_data', '0');
INSERT INTO cpg15x_config VALUES ('read_iptc_data', '0');
INSERT INTO cpg15x_config VALUES ('reduce_watermark', '0');
INSERT INTO cpg15x_config VALUES ('registration_captcha', '0');
INSERT INTO cpg15x_config VALUES ('reg_notify_admin_email', '0');
INSERT INTO cpg15x_config VALUES ('reg_requires_valid_email', '1');
INSERT INTO cpg15x_config VALUES ('report_post', '0');
INSERT INTO cpg15x_config VALUES ('session_cleanup', '0');
INSERT INTO cpg15x_config VALUES ('show_bbcode_help', '1');
INSERT INTO cpg15x_config VALUES ('show_private', '0');
INSERT INTO cpg15x_config VALUES ('show_which_exif', '|0|0|0|0|0|0|0|0|1|0|1|1|0|0|0|0|0|0|0|0|0|0|0|1|0|0|0|1|0|0|0|1|1|0|0|0|0|1|0|0|0|1|0|0|1|1|0|0|0|0|0|1|0|1|1');
INSERT INTO cpg15x_config VALUES ('silly_safe_mode', '0');
INSERT INTO cpg15x_config VALUES ('site_token', MD5(RAND()));
INSERT INTO cpg15x_config VALUES ('form_token_lifetime', '900');
INSERT INTO cpg15x_config VALUES ('slideshow_hits', '1');
INSERT INTO cpg15x_config VALUES ('slideshow_interval', '5000');
INSERT INTO cpg15x_config VALUES ('smtp_host', '');
INSERT INTO cpg15x_config VALUES ('smtp_password', '');
INSERT INTO cpg15x_config VALUES ('smtp_username', '');
INSERT INTO cpg15x_config VALUES ('subcat_level', '2');
INSERT INTO cpg15x_config VALUES ('tabs_dropdown', '1');
INSERT INTO cpg15x_config VALUES ('theme', 'curve');
INSERT INTO cpg15x_config VALUES ('theme_list', '0');
INSERT INTO cpg15x_config VALUES ('thumbcols', '4');
INSERT INTO cpg15x_config VALUES ('thumb_height', '128');
INSERT INTO cpg15x_config VALUES ('thumb_method', 'im');
INSERT INTO cpg15x_config VALUES ('thumbnail_to_fullsize', '0');
INSERT INTO cpg15x_config VALUES ('thumb_pfx', 'thumb_');
INSERT INTO cpg15x_config VALUES ('thumbrows', '3');
INSERT INTO cpg15x_config VALUES ('thumb_use', 'any');
INSERT INTO cpg15x_config VALUES ('thumb_width', '128');
INSERT INTO cpg15x_config VALUES ('time_offset', '0');
INSERT INTO cpg15x_config VALUES ('transparent_overlay', '0');
INSERT INTO cpg15x_config VALUES ('unsharp_amount', '120');
INSERT INTO cpg15x_config VALUES ('unsharp_radius', '0.5');
INSERT INTO cpg15x_config VALUES ('unsharp_threshold', '3');
INSERT INTO cpg15x_config VALUES ('upl_notify_admin_email', '0');
INSERT INTO cpg15x_config VALUES ('upload_create_album_directory', '0');
INSERT INTO cpg15x_config VALUES ('upload_mechanism', 'swfupload');
INSERT INTO cpg15x_config VALUES ('user_field1_name', '');
INSERT INTO cpg15x_config VALUES ('user_field2_name', '');
INSERT INTO cpg15x_config VALUES ('user_field3_name', '');
INSERT INTO cpg15x_config VALUES ('user_field4_name', '');
INSERT INTO cpg15x_config VALUES ('userpics', 'userpics/');
INSERT INTO cpg15x_config VALUES ('user_profile1_name', 'Location');
INSERT INTO cpg15x_config VALUES ('user_profile2_name', 'Interests');
INSERT INTO cpg15x_config VALUES ('user_profile3_name', 'Website');
INSERT INTO cpg15x_config VALUES ('user_profile4_name', 'Occupation');
INSERT INTO cpg15x_config VALUES ('user_profile5_name', '');
INSERT INTO cpg15x_config VALUES ('user_profile6_name', 'Biography');
INSERT INTO cpg15x_config VALUES ('user_registration_disclaimer', '1');
INSERT INTO cpg15x_config VALUES ('users_can_edit_pics', '0');
INSERT INTO cpg15x_config VALUES ('views_in_thumbview', '1');
INSERT INTO cpg15x_config VALUES ('vote_details', '0');
INSERT INTO cpg15x_config VALUES ('watermark_file', 'images/watermark.png');
INSERT INTO cpg15x_config VALUES ('watermark_transparency', '40');
INSERT INTO cpg15x_config VALUES ('watermark_transparency_featherx', '0');
INSERT INTO cpg15x_config VALUES ('watermark_transparency_feathery', '0');
INSERT INTO cpg15x_config VALUES ('where_put_watermark', 'southeast');
INSERT INTO cpg15x_config VALUES ('which_files_to_watermark', 'both');