this is going to seem pretty minor but it had me stumped for a while within the file /etc/modules.d/nvidia for nvidia-drivers 1.0.8776 the line #option nvidia NVreg_Mobile=1 which can be uncommented for mobile devices should be #options nvidia NVreg_Mobile=1 (the extra "s" makes all the difference when X hard locks) module-update doesn't seem to like "option", only "options" it took me ages to figure out why Mobile wasn't being set to 1 within /proc/driver/nvidia/registry when modprobing nvidia
*** This bug has been marked as a duplicate of 139756 ***