Comment 3 for bug 439551

Whatever it was that was causing xorg.conf to get truncated to 0 bytes has been fixed (though I suspect X still doesn't like that); however, virtualbox guest upgrades from jaunty to karmic without the virtualbox guest tools/drivers installed are result in an X server that fails, despite the existence of a seemingly okay xorg.conf file; see bug 457433 for details. Again, the workaround of removing the xorg.conf entirely causes X to start successfully.