Acrobat Professional 9.3 kept crashing on me when I would open more than 1 or 2 documents at a time.
Many thanks to LOTD for the suggestion of uninstalling acrobat and then deleting:
C:\Documents and Settings\"USERNAME"\Application Data\Adobe\Acrobat
Instead of uninstalling because I am lazy, I just renamed the below to old9.0 and created an empty 9.0 dir:
C:\Documents and Settings\"USERNAME"\Application Data\Adobe\Acrobat\9.0
I then was able to open up 20 documents at once w/o crashing. Acrobat recreated the missing files in 9.0. Just in case this was not the solution, I renamed the new 9.0 to something else and renamed the old9.0 back to 9.0 and tried the same experiment. It crashed as expected when it got to 2 or more documents. FWIW, between each experiment I killed any adobe task running in the background just to be safe.
Anyway, maybe this will solve my problem. Thanks for pointing me in the right direction.