Still happening here and it's unpredictable. I took my Macmini into the Genius Bar and both displays worked. I brought it home and both my LG monitors worked fine for a day. When the monitor I plugged into the HDMI port of the Macmini quit again I plugged a Viewsonic monitor into it and it worked. This worked for over a week and now the HDMI port of the Macmini is once again not sending a signal to the monitor. I tried plugging the Viewsonic into it again and this time the Viewsonic would not come on either.