Well if you want to use the previous version which have the security holes,
then copy the 6 files that was changed in pl1..
The pl1 was only 6 files, and NO upgrade scripting, but the error was bad enough
i saw it on vb.com they executed it there on a profile causeing popups in thta profile
now it was a true malicious person the popup could have contained bad stuff

luckly it didnt.
Howewer whats most importent closed security risk
or comments...
If comments, then simply find the mod that allow forumsthreads to be added for comments.
dont remember its name, but something as cms comments on forum.. ...
else wait for support, and make sure you have given them temp admin acces
while waiting, cause im thinking its a conflict you have with something else,
so its proberly unique to you and the others using the same conflicting unknown item.
Did a few cms posts which turned out great, and comments fine aswell..
do you have and CMS mods ?