Comment 22 for bug 583891

Two things; one I don't get the same problem running on Gnome without desktop effects rather than KDE with desktop effects; haven't tried the two in between.

-12 is -ENOMEM and I've traced it back a little:

Oct 4 13:11:27 major kernel: [ 795.810631] [drm:ttm_bo_validate] *ERROR* ttm_bo_validate: ttm_bo_move_buffer gave ENOMEM
Oct 4 13:11:27 major kernel: [ 795.810634] [drm:radeon_bo_list_validate] *ERROR* radeon_bo_list_validate: ttm_bo_validate gave NOMEM
Oct 4 13:11:27 major kernel: [ 795.810636] [drm:radeon_cs_ioctl] *ERROR* Failed to parse relocation -12!