Comment 7 for bug 118225

Here are a few different things to try:

1. Run "sudo dpkg-reconfe xserver-xorg", and choose only the 640x480 mode (or the 800x600 mode)

2. Install and run displayconfig-gtk
     sudo apt-get install displayconfig-gtk
     sudo displayconfig-gtk

     Use this tool to select the correct graphics card and monitor. Hopefully displayconfig-gtk will auto-detect them, but if not you can select them from the GUI. You might try selecting Plug 'n' Play. note that this is a new program very early in development, so it has bugs and may not work at all. But it would be great if it can do it.

3. Tell me the make and model of your monitor, and the output from these commands, and I'll do some more investigation:
    discover --disable=serial,parallel,usb,ide,scsi --format="%V %M\t%S\t%D\n" video
    sudo ddcprobe
    sudo xresprobe vesa