Comment # 16 on bug 73848 from Marti Raudsepp

(In reply to comment #15)
> If you disable acceleration (add Option "NoAccel" "true" to the device
> section of your xorg config) do you still get the problems?  It's most
> likely some issue related to the 3D engine set up in mesa.

You're right, NoAccel true also fixes this issue.