"HTTP-500 error -internal server error". When trying to post in 1 forum only
 

Hi

This is a sporadic problem. Affecting some visitors some of the time in only 1 of my forums.

"HTTP-500 error -internal server error".

A member will try to create a thread and get that error. If I log into their account (when they've PM'd me to report it) I don't get the error. They can create threads in any of the other forums.

Any ideas will be much appreciated.