Don't know the right name for the damn thing, but the kind of stuff you use to plug in various computers to use a single monitor and just switch them around or vice versa.
It's kind of like a hub for input/output devices, a friend of mine has one that has like 4 VGA inputs and 4 PS2 inputs.
I hope you understood something from that shithole of an explanation.
Also, are you trying to use it as a clone or streching the screen to/from the projector? I had something like that happen to me once when i couldn't for the life of me make the damn projector work in clone mode, it got that same way you described, but it worked fine as a streched space of the desktop.
All work and no play makes me..., well, you know the rest.