Strange Issue using Integrated Graphics

Hi guys,

I'm facing a strange issue with my MB Pro mid-2010 w/ ML.

It was all fine until yesterday, but since today when using Integrated Graphics(Intel HD) my screen starts to glitch, showing only a distortion of the screen, but when going back to the dedicated NVidia GT 330M it 's normal.

Could this be a OSX ML problem or is it probably my graphics card?