I am running IE 7.0 and lately it has been crashing a lot (only on this site). It usually happens after opening an external link in a new window, then after closing that window I get an IE error message and the whole thing shuts down.
I also noticed it has been blocking an ActiveX control that wants to run on the site. I just recently allowed it to run and still got an error/crash.
I occasionally run IE 7, beta 3 at home and at work (mostly, though, I use Opera), but I’ve never encountered the problems you’re having. You might make sure you’re up-to-date with the latest beta.
As for ActiveX, I know previous versions of vBulletin used ActiveX for the WYSIWYG Editor, but I’m not sure if that’s true anymore.