It took me a while to track this down, so I thought I'd share it.
When copying files in Explorer, I started getting a "Windows Explorer has
stopped working" error message and the program would shut down. The problem
is caused by programs that add themselves to the context menu, i.e. when you
right click, you'll see an entry for that program.
I used a free program called ShellEX (
www.nirsoft.net/utils/shexview.html)
to remove suspect context menu additions. You must run ShellEX as
administrator. Though I removed a number of them wholesale, I suspect the
problem program was iTunes.
Once these extraneous context menu additions were removed, the Explorer
crashes stopped and everything runs as it should.