I had no problem with nvidia card and suddenly lost driver... I tried everything in the Internet with no luck. I removed, reinstalled, etc.
The card is nvidia c67 geforce 7000m / nforce 610m] rev a2 Could you guide me through.
Go to the ubuntu software center.
Click "edit" and select "software sources".
Now, click on the "additional drivers" tab.
Here, you will be given the option for which driver to use. You can choose to install the nvidia proprietary driver or use nouveau.
If you are using the nvidia proprietary driver and are unhappy with the resolution of Grub2, your splash screen, and the tty terminals, see here https://askubuntu.com/a/594946/167115