Comment 21 for bug 49827

It turns out there's several distinct bugs being glommed together into this one.

bug 27667 affects LCD's and results in their top most (usually preferred) resolution being ignored. My fix for 27667 should solve this. If you know your VGA-attached LCD or CRT monitor supports exactly 4 resolutions, which include 1024x768, 800x700, 640x480, and one more that is bigger than 1024x768 but which is missing, then this is probably your bug.

Some other proportion are seeing 94994, which occurs when the monitor doesn't report its edid properly. I suspect this is because xresprobe only supports edid 1.0 style data, and some (newer) monitors report only in edid 2.0 format. However I've not confirmed this. If you suspect you fall into this category please review 94994 and help test.

I've also noticed that gnome seems to display the three resolutions 1024x768, 800x600, and 640x480 as defaults when it wasn't able to determine the correct resolutions. If you know your monitor supports far more than these three, but only these three are available, then you have this one. Unfortunately, this is just a symptom of what's really wrong with your system; the root cause could be a variety of things. Check your output on "sudo xresprobe <driver>", "sudo ddcprobe", "sudo get-edid | report-edid", verify the driver in xorg.conf is correct for your hardware, and report your findings here.