I looked at what restore points I have and found that sometime today I had updated the flash player from 10.x (that comes with CS5) to 10.1.82.76. I could roll back just that change (no windows updates). Problem gone.
So I reinstalled the flash update: no problem. Installed the one windows update that was due: still no problem.
So I'm back to work and won't worry about it unless it comes back.
My guess would be that one bit/byte went bad during the install... maybe during unpacking or maybe the spot it hit on the hard disk had an instant's problem
At least the roll-back and reinstall took care of the issue (this time).
One thing to keep in the back of your mind, is that Win updates and hot-fixes can also hose the video driver instantly. Other programs might never notice this, but PrPro will likely, as it interfaces with that driver more closely, than almost any other program. Just something to tuck away, in case you have other issues in the future. It was moot this time around though.