Thank you for posting to the Microsoft Answers Forum.
As Suresh suggested, the best way to find what is causing the problem is with a Clean boot.
If the program doesn't happen in a clean boot, then it is being caused by some 3rd party software program or service.
You will have to investigate and try one at a time or in a group. It is a tedious process but really the only way to identify the conflict.
Click on the article number below:
929135 - How to troubleshoot a problem by performing a clean boot in Windows Vista or in Windows 7
There is some discussion about Mozilla Firefox 3.5.5 may be causing a issue and going back to an earlier version doesn't cause an issue with Explorer crashing.
Some antivirus such as could be causing a problem. It is really just going to be trial and error.
Please reply back with an update as it may benefit others.