Why Can't I See Any Point Clouds?

I'm on Windows XP Professional v2002, with SP2, Nvidia Quadro4 980 XGL, 2.66Ghz processor, 2 GB of RAM. Downloaded and installed Photosynth yesterday. Everything seems to be working fine, except I can't see any point clouds. Toggling "P" key brings up only a black screen. This is consistent in every synth I load. I've tried both I.E 7 and Firefox 2. I've rebooted multiple times, etc. No go. I'd really like to see one of these point clouds. Any ideas?
Thanks,
George