Maybe I'm missing something obvious but here goes.
When I can I'll use a 19" monitor via HDMI to monitor shoots.
Recently I captured some footage on my MAC -
HDMI out the HMC to my BlackMagic intensity pro.
Ever since that shoot the HDMI out on the camera only works on select TV's one of them is NOT my monitor.
I've pluged the HDMI cable into about 5 different TV's and it worked on 2 of them. the others show 'unsupport'.