Problem with projectors and 12" powerbook


I have a 12" PB. I hooked it up in our seminar room yesterday to the A/V console. The ceiling mounted projector is an NEC-brand projector, barely 1 year old. Well, the presentation was fine for about 2 minutes, then the projector started to lose the signal intermittently. After about 10 minutes, it was completely hopeless and couldn't hold the signal for more than a couple of seconds. Brought in my PC laptop (bummer---no Keynote) and it worked fine. Hooked the PB back up. No go. Tried the PB on an identical projector (but one that doesn't connect to the laptop through a switching box) in another room and it worked fine. Back to the original projector, worked for a minute or so, then started losing the signal again. Tried two other even newer projectors. No go. But they both worked with a PC. The problem definitely is at least related to the fact that I'm using a mac since the PCs worked in every case but it's weird that it works great on one projector and not on another. The only consistent factor seems to be that I can't get the PB to work with a projector for more than a few minutes if the signal is routed through a switching box (so that multiple computers can be used at the same time).

I combed through the archives of the forum but couldn't find anything like this. Does anyone have any ideas? Or a similar experience?