Comment 36 for bug 1301839

@Pali: I am glad it worked for you, but this is not an acceptable solution for less technical users who just want Ubuntu to work straight after boot.

I currently dual boot with Debian unstable, which is running kernel 3.13, mesa 10.1, xorg 1.15 and GNOME 3, and I have none of these problems. Both the opensource and proprietary drivers worked painlessly.

I don't know whether the probblem comes from Unity itself or the patched kernel that Ubuntu runs, but, as of today, I cannot use the opensource driver because of this bug and cannot use the proprietary driver because Unity refuses to load (same as reported here: http://www.phoronix.com/forums/showthread.php?93838-Ubuntu-14-04-Kernel-3-13-and-AMD-Catalyst-issue). The only option that works is with nomodeset (Unity running software acceleration), great !