(II) LoadModule: "nvidia"
[ 13.536] (II) Loading /usr/lib/xorg/modules/drivers/nvidia_drv.so
[ 13.536] (II) Module nvidia: vendor="NVIDIA Corporation"
[ 13.536] compiled for 1.6.99.901, module version = 1.0.0
[ 13.536] Module class: X.Org Video Driver
[ 13.536] (II) LoadModule: "nouveau"

может тут проблема?