beryl gives these errors:
libGL warning:  driver claims not to support visual...
No stencil buffer.  Clipping transforms.....
GL_ARB_fragment_program  missing

and I also get these errors after gdm quits:
[17276167.324000] [drm:i810_wait_ring] *ERROR* space: 65520 wanted 65528
[17276167.324000] [drm:i810_wait_ring] *ERROR* lockup
[17276170.336000] [drm:i810_wait_ring] *ERROR* space: 65512 wanted 65528
[17276170.336000] [drm:i810_wait_ring] *ERROR* lockup