Comment 16 for bug 274290

@Taco, sounds like you may have an unrelated issue.

@Hugo, looking at your logs (thanks for including all of them!) I notice it's picking out this resolution to use:

(II) RADEON(0): Output DVI-0 using initial mode 1400x1050

I'm wondering if the issue may be simply that this resolution is not working properly with your hardware. Perhaps the HW doesn't support it, or perhaps the xserver is associating an invalid modeline for it. Could you follow the 'Workaround' steps at https://wiki.ubuntu.com/X/Troubleshooting/Resolution and see if you can force it to start up on -ati with a lower resolution? If that works, then if that is a valid resolution for your hardware we should investigate why it didn't work; if it's not a valid resolution we should figure out why it's being selected.