iPhone 3G blacks out and displays random static Last night the iPhone 3G (my friend's iPhone, not jail-broken) went black and a white fuzzy line would move around the screen.

Powering off and starting again seemed to remove the problem.

We have not been able to reproduce the problem since yesterday. What hardware/software fault could be a likely cause for this?  So it would be possible to tell an Apple Genius next time it happens.
It's the display connector cable inside the iPhone which can come a little loose. You can open it up and reseat the cable if it happens again. Ifixit.com have guides.