Seeing the same thing here, on Ubuntu 12.04. Graphics adapter (lspci) is "Advanced Micro Devices [AMD] nee ATI Caicos [Radeon HD 7000 Series]", xserver-xorg-video-ati at "1:6.14.99~git20111219.aacbd629-0ubuntu2".
The "start lightdm" workaround works for me aswell, although I have to *re*-start it, as it claims to be already running.
Seeing the same thing here, on Ubuntu 12.04. Graphics adapter (lspci) is "Advanced Micro Devices [AMD] nee ATI Caicos [Radeon HD 7000 Series]", xserver- xorg-video- ati at "1:6.14. 99~git20111219. aacbd629- 0ubuntu2" .
The "start lightdm" workaround works for me aswell, although I have to *re*-start it, as it claims to be already running.