Database error when submitting new thread

[itsheinz]

Guys help me.Ive been experiencing databse error after submitting a new thread.
What seems to be the problem...help me.My members cant create a new thread in my forum.

[stonesy]

Post the database error here from your logs

[snakes1100]

When you get the db error on the screen, post what the error says, if it dont display, right click the page and select view source and copy the db error message.

[itsheinz]

this DB error appears:
Database error in vBulletin 3.8.1:

Invalid SQL:
UPDATE user SET current_exp=current_exp+a WHERE userid='1';

MySQL Error : Unknown column 'a' in 'field list'
Error Number : 1054
Request Date : Monday, April 6th 2009 @ 07:04:42 AM
Error Date : Monday, April 6th 2009 @ 07:04:44 AM
Script : http://www.myforum.com/newthread.php?do=postthread&f=16
Referrer : http://www.myforum.com/newthread.php?do=newthread&f=16
IP Address : 89.108.47.244
Username : heinz
Classname : vB_Database
MySQL Version : 5.0.67-community

What seems to be the problem?

[snakes1100]

Disable your plugin system in the admincp --> vbulletin options --> plugins

See if the issue is gone after doing so, if it is, you will need to re-enable the plugin system, disable each plugin 1 by 1 until it goes away again, remove the bad hack/addon that you installed.