This is a recent thing that happened. I don't know what is causing it and chances are I am going to have to take this to the apple store :/ Anyways, basically I have been using my MBP with my monitor and it has worked flawlessly. This weekend it decided to start acting up, it's not outputting and video signal. It will work fine for a while and then it just cuts out, I also noticed that if I slightly tap to the left of the trackpad the monitor flickers. I'm assuming that perhaps its the video card stuff and maybe there is some overheating going on? Some feedback would be much appreciated! Thanks!