Since you're running S-Viceo, my first guess would be a bad cable. S-Video has two lines, one for image and the other for color information.
My second stab would be that your laptop doesn't have enough memory to drive both displays reliably. Running video takes more resources. Try disabling the laptop's display when running. This, of course, assumes that you are trying to drive both displays at the same time.
|Quote (gap123 on Jun 29, 2008 11:59 AM):|
I have a viewsonic pj503d
while running movies from my laptop via S-video cable, the picture changes back and forth from black and white to color