Forum Database error while posting a new thread? Plz help!!

[محروم.كوم]

When I want to post a new thread on my vBulletin 4.0.6 PL1 forum, it gives database error. Especially when I add an image or link in the post. And when I only write a simple text and post it, everything is OK. What could be the problem here?

Here is the database error:

Code:

Invalid SQL:

SELECT data, expires, locktime, serialized
FROM cache
WHERE cacheid = 'vb_types.types';

MySQL Error : MySQL server has gone away
Error Number : 2006
Request Date : Friday, September 10th 2010 @ 09:34:46 AM
Error Date : Friday, September 10th 2010 @ 09:35:21 AM
Script : http://www.site.com/newthread.php?do=postthread&f=288
Referrer : http://www.site.com/newthread.php?do=newthread&f=288
IP Address : xx.xx.xxx.xx
Username : xxx
Classname : vB_Database
MySQL Version : __DEFINE_LIKE_SHARE__