Video playback flashes blank for a split second.

I have a mac mini Mid 2010 running OSX Mountain Lion. It just started having an issue with video playback on DVD player and iTunes. It flashes a grey and white checker board like the background thats represents transparent pixels. It last for only a split second but happens randomly during playback, very annoying.

Has anyone seen this? is this a known issue? Could it be hardware or software?

Thanks,