Having recently installed a new version of Linux I thought I'd see how progress on Compiz, the compositing window manager, was going. I tried it first on a system with an ATI video card and was met with a wonderful blank screen. Since I really didn't want to spend a bunch of time trying to figure out what was going on I just put things back to normal and got X working again.
However, before I gave up completely I thought I'd try it on a system I have with an NVidia video card. Set things up on it, and... same result, blank screen. And this is where it gets interesting: I put things back as they were before and I still got a blank screen. So, I figured I needed to try the Windows solution: reboot. I shut the system down, unplugged it for a few seconds just to be sure and booted. And... still a blank screen, and I mean blank, no BIOS screen, no nothing.
Checked the monitor on another system and it was working fine. Seemed unlikely that Compiz had actually fried the video card but that's what it was looking like.
Since the video card had both a DVI and a VGA output I thought I'd try a monitor with a VGA connector rather than a DVI connector. That worked! Booted, got the BIOS screen and X. Figured maybe whatever had been boinked on the video card was now reset so I tried the DVI again. Now the DVI worked, although the BIOS screen was horribly stretched across the screen, but it booted fine and started X without problems and everything has been fine since.