Unfortunately that seems to happen from time to time. It depends on the processor power in relation to what you are trying to do I think. My faster laptop with Windows 7 rarely gets a problem but my older desktop does get it more frequently.
It is really annoying, as it is when your screen fills up with repeated memory address errors at about 50 messages boxes per second until you can Ctrl Alt Del and kill the process - anyone else get this ?
Alfaman