Registry Compacting doesn't change the contents of the registry in any ways, so I don't know whether it would be possible that simply compacting the registry could cause this.
Take a look at these:
http://phorums.com.au/archive/index.php/t-139188.html
http://www.hftonline.com/forum/showthread.php?t=16321
It seems like the problem has something to do with ATI's drivers.