Hello,
I installed Ubuntu Server 64bit 12.10 on a Dell Poweredge T20 and wanted to run it headless, but I ran into the following problem, that when no monitor was attached, or if you send the system into standby and wake it up again, the screen is black if connected via VNC. I found this old thread: https://software.intel.com/en-us/forums/topic/279956 where it was suggested to add "nomodeset" to GRUB config, which I did, and it seemed to work at first. I now got a VNC signal too after standby wakeup, but now the mouse/keyboard doesnt work anymore. The video picture still works, because I can see the time changing on my Ubuntu desktop, but the VNC doesnt accept any mouse nor keyboard input anymore. When I reboot, the issue is gone, but the moment I do the same, send the system into standby via pm-suspend, wake it up again via WOL, it's broken. I also noticed, that the nomodeset option results in the video driver not working anymore correctly (with hardware acceleration), because I see large CPU consumption of "Compiz" and X server.