I had the same issue and reinstalling nvidia-173 worked for me also.
More details for new users:
When booting, the symptoms are: you see a list of events with [OK] or [fail], and then nothing further happens. I had several [fail], apparently unrelated. Linux has tried to start X windows (the graphics display) and failed, quietly. Now if you enter Ctrl-Alt-F1, Linux starts a terminal (a non-graphical command line.) Linux is running, just without graphics. You can examine the file /var/log/Xorg.0.log to find the error:
(EE) NVIDIA(0): Failed to load the NIVIDIA kernel module!
Then, enter as described earlier:
$ sudo apt-get install --reinstall nvidia-173
Note it is not just install, but a --reinstall. Linux downloads it from the net, compiles it and installs it. Then reboot.
Then Ubuntu should start. I got an alert that new proprietary drivers were available. I started System Settings>Harware>Additional Drivers. It showed that a "version current" was the recommended version but that "version 173" was installed. I don't think it matters (both seem to fully use the graphics card) but I chose "version current" and the "Activate" button. Then restarted. That version (whatever it is?) also seems to work.
Possibly you can forestall the alert that new drivers are available by installing "nvidia-current" the first time?