I've noticed that Vista (on my laptop anyway) misinterprets applications (such as Leveller) that undertake long processes so that the "Not Responding" phrase appears in Leveller's title bar and the app window seems frozen. It doesn't seem to matter that the processes are interruptible and regularly update the display (including responding to paint events).
This happens sometimes when raytracing. The first render may go perfectly fine, but eventually some subsequent render will appear to freeze even though Leveller is still processing normally. Pressing Esc won't stop it but waiting for it to finish will work. The display may also show artifacts or pieces of previous displayed information.
I suspect Vista is overly aggressive about long processes that ignore the main event loop and starts seeing them as non-responsive. But putting all long processes on background threads is not something that can be implemented quickly. In the meantime, however, simply waiting for the process to end will work.
A search on Google shows numerous other "not responding" issues for Vista, but I'm not sure if there is a relationship to the problem I'm describing here.
Ray
