Date: 15-11-05 20:48
Try forcing your mode to something you know is available, like 640x480, in your Display subsections of your xorg.conf. I ran into a case recently where a dell 19" flat panel was not correctly communicating its maximum resolution and the Xserver attempted to drive it at 1600x1200. Since the real max res of the device was 1280x1024, the server never died but the signal sent to the monitor was out of range and it switched off.
Viewport 0 0
If this works, go ahead and throw in all of the known supported resolutions for your display hardware.