Change your hardware acceleration and turn off other programs you might have
open.
How to set graphics hardware acceleration back
http://www.rdpslides.com/pptfaq/FAQ00129.htm
I see this occur fairly often when I have, oh, Outlook, Outlook Express,
PowerPoint, Illustrator and Word all running.
I used to see it even when I'd have nothing running, but if I had something
like SETI going in the background. So if you have any distributed computing
apps, I'd disable them (at least when working on PPT).
