I have a year old 17" MBP. I use it with a 24" Dell and have had no problems. Occasionally I hook it up to my HDTV with a long HDMI cable and a DVI to HDMI adapter. Tonight I wanted to watch something so I unplugged the Dell and plugged in the TV, but nothing happened. I noticed on my MBP everything was on the one screen as if dual display was not working. I unplugged the mini display port, screen goes blue for a sec, and the same screen comes back up. Plug it back in, screen goes blue for a sec, and the same screen comes up. Repeat, same results. The Dell when unplugged says "no dvi signal" but plugged in is black. Restarted 3 times, repaired permissions.... nothing. Has anyone else encountered this?