I have a Macbook Pro Retina Mid 2012 Edition. Running the Nvidia GeForce GT 650M Graphics card. OS X 10.8.4 I bought an LG Monitor the other day, plugged it in to my mac, didn't pick it up, plugged it into my PC to see if I had to set it up for some reason, and then back to my mac.. Worked fine! Decided to play one of my PC only games and connected my monitor back to it, after I was done I plugged it back to my mac... and now it isn't picking it up at all. My screen on my mac flashes blue like it knows it was connected to something else, but outside of that nothing else happens. My monitor says "hdmi no signal" and I have tried multiple HDMI cords as well. Although it cannot really be the HDMI cord problem as they do work with my PC and other things as well. I am connecting the HDMI directly through my Mac and not through a DVI<HDMI port. Considering my Mac has an actual HDMI port. I just don't know what to do in order to get the monitor working again, as it was working previously... Any help would be greatly appreciated.