My 12" Powerbook G4 lately has been behaving strangely when using the mini-DVI port. I'm using the Apple TV Video adaptor (the one that lets you use an RCA cable) to connect my laptop to a television (for watching DVDs and such). But lately, whenever I plug the adaptor into the mini-dvi slot, my laptop screen will go blank--and then remain that way. It used to go blank for a second, then come back on with the Television as well--now when I connect the TV I only get picture there, and no longer on my actual computer screen. Any ideas as to why this might be?