Windows 7. Dual Core cpu.
After about 3 hours heavy use the PM window went fuzzy and mouse is busy. After about 10 minutes of this I hit the X button and it asks if I want to wait or close. It closes, eventually, and I can restart. It has done this to me before. I was attempting to do a copy at the time. The bad news is on restart all the folder setting had reverted to the last time I used it.
The folder has 750 images but the previous folder had over 1000 which I had processed earlier.