Any thoughts on this problem with dual monitors

I am running both FS9 and FSX. I have set up two monitors using a Nvidia XFX 7800 video card. FSX runs fine, In fact FSX is dual monitor friendly. It's just a drag and drop to move the GPS, radio, and other windows to the second monitor. The problem is if the two monitor desktop is running, FS9 does not display the aircraft in the preview window. If I turn off the dual monitors it works fine. I don't really want to keep change my Nvidia setup every time I want descent frame rates and fire up FS9. Thanks