There seems to be something odd about the HDMI output from my Hero2. My HDMI monitor only receives a signal if I have the minijack cable plugged into the A/V-out socket.
Surely this can't be right, or is it?

I've used my Hero2 many times with a SmallHD monitor and a Marshall. It works fine on either with nothing but the HDMI cable plugged in.

Must be a monitor problem, I've just tried it on my TV and it's fine with just the HDMI.