Great guide. But when i run the command:

root@ricky-N53Jf:~# optirun glxspheres
[ERROR]Cannot access secondary GPU – error: Could not load GPU driver

[ERROR]Aborting because fallback start is disabled.

I have an ASUS N53JF with NVIDIA OPTIMUS, the strange is when i start with the live CD all go the best: i have the graphics effect. After the installation and the reboot ubuntu 12.04 have only 2D graphics. I follow your guide and the guide proceed with no problem (no error) but now i can’t use the discrete card. You know why? There’s a method to restore the installation equal to LIVE CD ? Thanks in advance and excuse me for my bad english.