PCA don't blocks programs, but instead changes its compatibility settings in an attempt to make them work with Windows 7. In your case, triggering it may be just a "false positive" due to the crash (PCA guessing that it crashed because of Windows 7, instead of a bug in the program). Just ignore it, and say it worked correctly if ever asked again. If you've touched any settings or let PCA to apply its changes at will, go to the compatibility tab of the main executable and disable compatibility mode.
Personally, I always disable PCA, as it only creates more problems than it solves and a lot of annoying popups. I have yet to see it correctly fixing a program. Program Compatibility Assistant - Enable or Disable