[Deathmaker]

OK, what monitors are you using? CRT, LCD, what resolutions, refresh rates?

It sounds like, as someone already said, that you're trying to display a res that the problem monitor cant handle.

As someone else has already said (you are listening to advice being given and acting on it, aren't you?) connect to the monitor you know works, set the res & refresh rate low, reconnect the dodgy monitor & if it works you know that was your problem.