First off, thanks for creating this useful site. Many times I google and it brings me here.
I have been using combofix on the odd occasion for a few months. Really a great piece of software as is dial-a-fix. Usually after a cleanup run (it hasn't failed me yet) I get explorer crashes. This problem has been on my mind as the last time it happened I ended up reinstalling windows (very time consuming, annoying and boring). This time around combofix found a rootkit, cleaned it and explorer started crashing.
The symptoms were if any folder/foldershortcut or recycle bin was opened from the desktop closing the window would crash explorer and it would restart. The same folder if opened/closed from the start menu would not crash.
After much investigation and time spent looking at filemon traces (I suspected that some explorer extension was either corrupted or deleted) I discovered that Free Download Manager was the culprit. Disabling/re-enabling monitoring in 'download options-> monitoring' seems to have fixed the problem (hooray!).
As an aside another app that causes explorer crashes (just by installing it) is winmount version 3.
Hope this helps someone.