Just a shot in the dark but I've fixed some pretty weird problems in
the past by doing the following:

1. Uninstall application
2. Delete any residual files and directories
3. Uninstall Internet Explorer (yes I know it sounds weird)
4. Run RegClean or another registry cleaner
5. Reinstall Internet Explorer and it's patches
6. Reinstall application

I also reboot anytime I uninstall or install IE even though I'm not
supposed to have to do that.

If you don't have all the patches for your version of IE AND you don't
have a high speed Internet connection then I'd say try something else
first as the IE patches can be big.