I have found a systematic error in the sessions table. The "ses" sessions table
occasionally report that the table has crashed. Due to this nothing can be displayed;
the entire forum is just blank.
Finding a source bug could be difficult, and if this is a hard-drive problem
nothing can be found. I suspect that a hacker-script enter some special
angry URL, and the session number is transferred to the database and some error
occurs. I have the logs, but I don't know what to look for.
The solution that I use now is that I "drop table" and then create a new empty
one using an SQL obtained from a forum that still works.
My thought is that:
To test-read the table, and monitor the error codes.
If the table is plain inaccessible, drop and then write
a new table by an external script.
There might also be problems with other tables that are updated frequently,
but I have not detected any problem elsewhere.
This issue is addressed on the wiki at performance tuning (see section about "database performance").
We've also made some changes to the session handling code in 3.0.5, so it might be worth your while to upgrade. FUDforum 3.0.5 also contains a Session Manager ACP to help you monitor sessions.