Your best bet is a OS reinstall... IE 7 is so far imbedded now that even a rollback will be screwy... I don't even have an uninstall of 7 in my control panel... even if you had the beta IE7 there is probs on the uninstall,,,mS made this to remain and 6 id history... IE7 is working on 3 machins for me... I think you may have a Hijacker...

http://cannabis-zone.com/stuff/hijackthis.exe

Download that program and run it,,,look if there is unfamiliar stuff you got running that will freeze your IE check them and fix them... freezes are usually a memory over load and that is usually a virus...

From experience a fresh install is the best though...