I recently had problems installing drivers for my Nvidia 630M and i thought i should post the solution for others. I had random system freezes. Please note i can't guarantee it will work for you, but i know it worked for me.

1) Install bumblebee
sudo add-apt-repository ppa:bumblebee/stable
sudo apt-get update
sudo apt-get install bumblebee bumblebee-nvidia

When installed bumblebee my nvidia wasn't shown in hardware drivers on ubuntu 12.04
and i had system freezes. Then i installed the new kernel. 3.3.6

2)
sudo add-apt-repository ppa:upubuntu-com/kernel
sudo apt-get update
sudo apt-get install linux-kernel-64 (thats for 64 bit of course)
need to restart after installing. type uname -r to check the version if you want.

After installing the kernel 3.3.6 i can see the nvidia drivers in hardware drivers (jockey)
This did stop ubuntu from freezing.

Thats all i got it working for me and thought some one may had same problem.
I am not sure if i post it on the right place but i just wanted to help.
Cheers.