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See here: http://torque.oncloud8.com/archives/000151.html

Acrobat ends up with 65,535 Acrxxxx.tmp files in your temporary directory and loses its mind:
Documents and Settings\[user profile]\Local...

I have the same problem. You described it very well. The only thing I would add is that a reboot brings the machine back to the state where 1 pdf can be opened.

I'm running a clean install of...