We've been having the same issue for about a month now.  I have gone as far as wiping a PC and reinstalling everything fresh, but days later the issue came back.  Talk about a waste of time. It does seem to happen when navigating a file structure in or outside of QB that contains QB files.  Leads me to believe it's the QBVersionTool DLL that tells explorer what version of QB to open each file with that is causing this disaster.

Does anyone have a way to roll back to before the R5 patch as a method of testing this?  

Here's a quick snippet of the # of crashes on 1 machine over the past few days to give some indication as to how bad this has gotten.