You need to make the database field that holds the mime type larger and then add the open office mime types to the filetypes table. Using phpmyadmin:
ALTER TABLE CPG_filetypes CHANGE `mime` `mime` VARCHAR(70) default '';
INSERT INTO CPG_filetypes VALUES ('odt', 'application/vnd.oasis.opendocument.text', 'document', '');
INSERT INTO CPG_filetypes VALUES ('ods', 'application/vnd.oasis.opendocument.spreadsheet', 'document', '');
INSERT INTO CPG_filetypes VALUES ('odp', 'application/vnd.oasis.opendocument.presentation', 'document', '');
INSERT INTO CPG_filetypes VALUES ('odg', 'application/vnd.oasis.opendocument.graphics', 'document', '');
INSERT INTO CPG_filetypes VALUES ('odc', 'application/vnd.oasis.opendocument.chart', 'document', '');
INSERT INTO CPG_filetypes VALUES ('odf', 'application/vnd.oasis.opendocument.formula', 'document', '');
INSERT INTO CPG_filetypes VALUES ('odi', 'application/vnd.oasis.opendocument.image', 'document', '');
INSERT INTO CPG_filetypes VALUES ('odm', 'application/vnd.oasis.opendocument.text-master', 'document', '');
INSERT INTO CPG_filetypes VALUES ('ott', 'application/vnd.oasis.opendocument.text-template', 'document', '');
INSERT INTO CPG_filetypes VALUES ('ots', 'application/vnd.oasis.opendocument.spreadsheet-template', 'document', '');
INSERT INTO CPG_filetypes VALUES ('otp', 'application/vnd.oasis.opendocument.presentation-template', 'document', '');
INSERT INTO CPG_filetypes VALUES ('otg', 'application/vnd.oasis.opendocument.graphics-template', 'document', '');
INSERT INTO CPG_filetypes VALUES ('otc', 'application/vnd.oasis.opendocument.chart-template', 'document', '');
INSERT INTO CPG_filetypes VALUES ('otf', 'application/vnd.oasis.opendocument.formula-template', 'document', '');
INSERT INTO CPG_filetypes VALUES ('oti', 'application/vnd.oasis.opendocument.image-template', 'document', '');
INSERT INTO CPG_filetypes VALUES ('oth', 'application/vnd.oasis.opendocument.text-web', 'document', '');
Change CPG_ to your actual mysql table name prefix during installation.