[ubuntu] MacBook 7, 1 screen goes psychedelic on Ubuntu 12.04

Hi there

I'm running 64 bit Ubuntu 12.04 on my MacBook Pro 7, 1. Periodically, the screen goes psychedelic (segmented, multicoloured static is splashed over the screen). This behaviour does not occur in Unity 2D but does occur in Unity. Has anyone else observed this behaviour? Could anyone point me in the right direction on how to prevent this from happening?

Thanks for any assistance