Colours distorted on video playback - iTunes 11

Since upgrading to iTunes 11, video playback has totally distorted colours, and also colours in the iTunes Store are distorted. I have tried reinstalling iTunes and Quicktime which didn't help. I am running iTunes 11.0.1 on a 64 bit Windows 7 Home Premium PC.

I have no problem playing video/DVD with any other software.

Any thoughts or suggestions welcome!