A colleague of mine is using dual monitors and one kept on going to sleep after saying 'DVI: no signal' each time we attempted to turn it on. I switched the VGA and DVI connections between the two monitors and they are both working fine now so the problem appears to have been the DVI connection on the monitor. I don't know much about these things though.

How could the DVI connection suddenly fail on what is a relatively new monitor (3 months)? What in particular would have failed and is it something that is easily replacable/fixable?