OK... the displayed screen now shows the real error:
mySQL error: Table './ntaliaco_copp3/cpg_mod_online' is marked as crashed and should be repaired
cpg_mod_online is not a core CPG table, it is added/used by a plugin onlinestats. It is also likely some external event caused the error - rather than plugin/mod code... but regardless should be able to fix from phpMyAdmin -where you turned on the debug option...
In phpMyAdmin:
Select table cpg_mod_online in the navigation pane on the left - Be sure the correct table name appears in the main frame when the page loads.
Then click the 'Operations' tab in the main frame - on lower left of frame (position may vary based on version of phpMyAdmin), are "Table Maintenance" options - click on Repair Table. You should get a message like 'Your SQL query has been executed successfully'
Try accessing your gallery again.
If other tables have the same issue - repeat the procedure for them. You successfully accessed a number of other tables before encountering the error per the debug trace. Typically I would expect only one table to be affected.
If all is well - turn off debug mode (at least for everyone) - via Admin Config (or via phpMyAdmin as you turned it on)
Additional information on repairing MySQL tables can be found at:
http://dev.mysql.com/doc/refman/5.0/en/myisam-repair.htmlhttp://dev.mysql.com/doc/refman/5.0/en/repair-table.htmlAs for what caused it - you can try providing the MySQL error message to your ISP - they may be able to find an error in the servers logs when the table initially 'crashed'.
Good luck!