Rich Text Editor Hangs and prevents editing - Firefox 12.0 Windows XP Prof 2002 SP3

[selvakumar]

Whenever I try to use the quick reply feature, the editor allows me to type but prevents any modifications.
I also observe this while trying to create new threads. I am able to enter the title but the editor doesn't allow me to post/edit the body.

I selected basic editor under general settings and it seems to be working fine. But any help to resolve the issue with the Rich text editor (WYSIWYG) is much appreciated

Environment : Firefox 12.0 running on Windows XP Prof 2002 SP3
Anti virus : Symantec End point protection