https://bugs.freedesktop.org/show_bug.cgi?id=28940
--- Comment #5 from Keivan shayanmansuri@yahoo.com 2012-04-11 14:33:36 PDT --- it's a very long time I'm wrestling with the very same issue with my mobility x1400. Today I found a workaround to did problem. I'm in kernel 3.2 of LMDE.
To solve this problem I forced my GPU into the maximum compatibility 3D acceleration mode with this simple xorg.conf
Section "Device" Identifier "Radeon" Driver "radeon"
Option "EXAPixmaps" "off" Option "AccelDFS" "off" Option "MigrationHeuristic" "greedy" EndSection