I just upgraded the forum to vBulletin 4.1.10. It's supposed to contain quite a number of bug fixes. I also took the opportunity to fix a couple of niggling style issues (such as fixing the borders for many of the header boxes).
One of the fixes is for VB-13545, which caused some bad behavior when using the cursor in edit boxes in FF8.
Please let me know if you are experiencing any new issues (or if old issues that are continuing to be problematic).
(If you do run into trouble, please try doing a hard refresh with Ctrl-F5 first.)