Null pointer exception when view a thread in standalone forum

Hi All,

I am using Enterprise Portal SP13.I installed two SCA file for Web Forum.

When I view a thread which was posted by some one or me,it throws Null Pointer Exception.

It happens some times not regulary.Somtimes its working fine.

Other things also when I delete a category and then create a category sometimes it throws Array Index OutofBound.

I am really confused.Is it bug for SP13?Should I upgread to SP20?

Syed