This sounds dubious at best, it's most likely the age old saying "the watched pot doesn't boil" and it only seems to take longer while you are waiting idly.

Could it have something to do with the way messages are processed by the window. For instance, I've seen cases where a lengthy process was undertaken, and the application developer used a progress bar to indicate the current progress. However, they were updating it far too often, which was causing a WM_PAINT to be fired over and over. In this case, you could speed the app up significantly by clicking and holding on the window title bar, which would keep it from wasting time on the redraw by plugging the queue. Again though, this was back in the bad old VB days with a bad old VB programmer.