I had installed the latest nvidia-driver package 173.14.31_3.2.53 NVIDIA drivers (non-free). Then I blacklisted nouveau. Rebooting: the nvidia driver was in use,nouveau not. But it did not work, black screen and this message in Xorg.0.log:
491.106] (II) LoadModule: "nvidia"
[ 491.106] (II) Loading /usr/lib/X11/modules/drivers/nvidia_drv.so
[ 491.107] (II) Module nvidia: vendor="NVIDIA Corporation"
[ 491.107] compiled for 4.0.2, module version = 1.0.0
[ 491.107] Module class: X.Org Video Driver
[ 491.107] ================ WARNING WARNING WARNING WARNING ================
[ 491.107] This server has a video driver ABI version of 12.1 that is not
supported by this NVIDIA driver. Please check
http://www.nvidia.com/ for driver updates or downgrade to an X
server with a supported driver ABI.
With nouveau the card works, resolution is ok, 1280x1024.
What does this mean in human understandable terms? ;-)