Ok, thanks for your reply :) So, this is what i have trying since my previous post (without success): 1 - Test only on the first screen like what you say. 2 - Switch the two screen physically and reconfigure the display configuration. 3 - Activate Sync to VBlank in OpenGL Settings (In the French Ubuntu documentation they indicate it can solve problem similar to mine) 3 - Desactivate the secondary screen but nothing change. :( Restart X server after every modifications. ps : visual effects (compiz) on my computer all works fine...
