Comment 22 for bug 16472

Happened to me when upgrading to hardy

The fix I used (which I haven't had to do in years, like before graphical logins ) is to reorganise the Modes in Section "screen" # of the xorg.conf so that the mode you want to use by default is the first in the list. eg :

original xorg.conf file using the wrong size 800x600 used but my display is 1280x1024

 Modes "800x600@60" "1280x1024@60"

change to

 Modes "1280x1024@60" "800x600@60"