i had issue where i could not get the resolution i wanted (1080p) and was locked to 1024x768 at most, and i only appeared to have the typical 4:3 resolutions. turned out it was a faulty VGA cable. swapped it and the correct resolutions were reported by mythbuntu.<br>
<br>while it doesn't sound like your problem, it might be worth a shot; be the quickest & easiest thing to test!<br>