Comment 6 for bug 556736

I've found that dkms seems to build "/lib/modules/($uname -r)/updates/dkms/nvidia-current.ko"
whereas xorg is looking for "/lib/modules/($uname -r)/kernel/drivers/video/nvidia/nvidia.ko"

My workaround is to create a symlink to point at the built driver:-

"sudo ln -s /lib/modules/($uname -r)/updates/dkms/nvidia-current.ko /lib/modules/($uname -r)/kernel/drivers/video/nvidia/nvidia.ko"

Substituting your kernel version for ($uname -r) of course.