Hi Jon. I had a similar problem after working with Pro/E for a while. Once out of nowhere an Internet Explorer ActiveX error popd-up and and I could no longer work with Pro/E (constant crashes right after opening it - same as your problem, I assume). For me restoring the OS (Windows) to it's previous state solved the problem for a while (short while) but the issue surfaced again. I was eventually forced to restore the system from a backup image I made early on (THIS IS SOMEWHAT EQUIVALENT TO REINSTALLING FROM WINDOWS CD) and reinstall Pro/E. After this I took the precaution of
disabling showing the browser window after Pro/E starts up Here is how: Note: you probably won't be able to do this right now, but take the info for future consideration.
This browser inside Pro/E uses the Internet Explorer engine and somewhere here the problem lies. By the way, 'Help' in Pro/E also uses this browser, so I dear not enter it too
Other then this, everything else I use seems to work fine! Contact PTC support for help! They should be able to help you find a workaround for you problem.