I know I've said a few times, but... HaCKeD doesn't work on 5D2. I'll remove it in the next release.
Hmm... I don't have a HDMI device, also I still don't know thoroughly how ML handle the HDMI signal. However it's possible to check if the HDMI is connected and we could do some HDMI special stuff.
btw
Today is Friday 13th 
It's definitely happened outside of Friday the 13th haha.
Unless you warm it out with recording a raw file without the monitor first, it will crash just after it empties the buffer from your recording. It freezes for a split second on the last green dot, and then the live-view goes off and the crash error is displayed.
My findings are that it does not crash if you both:
Record 1 raw before plugging in or powering up the external monitor.
Use a mode other than hacked after "warming" it up.
If you power cycle the device, and try again without "warming up" with a raw again, it will crash.
If you shut off live view after you've "warmed" it up and turn it back on, it will NOT crash.
It may or may not crash when going to the regular canon menu system.