I think problem might be with optimus. It means your pc has 2 graphic cards, one this NVIDIA and second is Intels integrated card. If so, you should take a look at bumblebee-project because linux does not support nvidia drivers, as far as i know. Guess you should reinstall ubuntu and this time avoid installing NVIDIA drivers, but instead install bumblebee, otherwise pc would heat a lot. Hope I helped.
Actually I think you can test for optimus by writing:
lspci | grep VGA
in console. If it shows intel and nvidia controllers like:
00:02.0 VGA compatible controller: Intel Corporation 2nd Generation Core Processor Family Integrated Graphics Controller (rev 09)
01:00.0 VGA compatible controller: NVIDIA Corporation GF108M [GeForce GT 540M] (rev ff)
then you have optimus.