I would try changing hardware acceleration on the 2nd monitor.
How to set graphics hardware acceleration back
http://www.pptfaq.com/FAQ00129.htm

Signature
Echo [MS PPT MVP] http://www.echosvoice.com
What's new in PPT 2007? http://www.echosvoice.com/2007.htm
Fixing PowerPoint Annoyances http://www.oreilly.com/catalog/powerpointannoy/
>I work with a laptop and have a 19" monitor and I usually extend the size
>of
[quoted text clipped - 8 lines]
> 19"
> monitor.