I suddenly had this "An SQL error has occurred. Please see error.log for details." and as usual visited the logs and saw...

06/22/06 20:08:19 - 1034: Incorrect key file for table 'gl_sessions'; try to repair it. SQL in question: DELETE FROM gl_sessions WHERE remote_ip = '66.249.65.42' AND uid = 1
06/22/06 20:08:20 - 1034: Incorrect key file for table 'gl_sessions'; try to repair it. SQL in question: DELETE FROM gl_sessions WHERE remote_ip = '66.249.65.42' AND uid = 1
06/22/06 20:32:08 - 1034: Incorrect key file for table 'gl_sessions'; try to repair it. SQL in question: DELETE FROM gl_sessions WHERE uid = 1 AND start_time
06/22/06 20:32:11 - 1034: Incorrect key file for table 'gl_sessions'; try to repair it. SQL in question: DELETE FROM gl_sessions WHERE uid = 1 AND start_time
06/22/06 21:53:08 - 1016: Can't open file: 'gl_sessions.MYI' (errno: 145). SQL in question: DELETE FROM gl_sessions WHERE remote_ip = '66.249.65.42' AND uid = 1
06/22/06 21:53:25 - 1016: Can't open file: 'gl_sessions.MYI' (errno: 145). SQL in question: DELETE FROM gl_sessions WHERE remote_ip = '66.249.65.42' AND uid = 1
06/22/06 21:59:58 - 1016: Can't open file: 'gl_sessions.MYI' (errno: 145). SQL in question: DELETE FROM gl_sessions WHERE remote_ip = '66.249.65.42' AND uid = 1
06/22/06 22:00:01 - 1016: Can't open file: 'gl_sessions.MYI' (errno: 145). SQL in question: DELETE FROM gl_sessions WHERE remote_ip = '66.249.65.42' AND uid = 1
06/22/06 22:00:02 - 1016: Can't open file: 'gl_sessions.MYI' (errno: 145). SQL in question: DELETE FROM gl_sessions WHERE remote_ip = '66.249.65.42' AND uid = 1
06/22/06 22:00:03 - 1016: Can't open file: 'gl_sessions.MYI' (errno: 145). SQL in question: DELETE FROM gl_sessions WHERE remote_ip = '66.249.65.42' AND uid = 1

then it's more or less the same after 22nd june...what can i do to resolved this? restore the db? anyway to repair it?

As the error message itself(!) already suggested: Try to repair the table. It's an option in phpMyAdmin, if you have access to that. Or find some other way to execute this SQL request: