Apple TV 2 - Picture Flashes

Hi there, I have a problem with my new Apple TV 2: every once in a while, the pictures blacks out for a split second, just barely noticeable. Sometimes it's only the upper half of the picture. Sometimes it's 10 minutes between two instances of this happening, sometimes it's 10 seconds.

It's not a streaming problem, as I can see the video has been buffered. And I've also seen this behavior on the main menu.

It's like if you would wiggle the HDMI cable.

Can anyone help me?