Comment 28 for bug 561789

I suggest, that you all try the workaround, Didier proposed.

Here's how to do that:

1. Press the power button of your computer
2. After the BIOS screen quickly press and hold the left shift key <-- http://en.wikipedia.org/wiki/Shift_key
3. Choose the recovery kernel (normally 2nd entry in the grub list
4. The recovery boot process will then start and after a while you will have a menu (blue background)
5. Choose the first entry 'resume' to resume the boot process --> boot process will then finish and you see a console login prompt
6. Login with your username and password
7. type sudo start gdm && exit <-- That command will 'start gdm' and log you out off the console, you are in ('exit')
8. You should now have a graphical interface.

If that workaround is working for you, then imho this bug is not related to the opensource ATI driver, but maybe related to plymouth involved in the boot process.