Workarounds are:
1 Switch off the HDMI control link on the TV. This means you will need to power on the TV separately and not automatically when the Humax comes on.
2 Unplug the HDMI cable from the TV and use the RCA (3 phono-like cables) - this seems to get rid of a lot of problems.
3 Be careful not to hold the POWER ON/OFF down too long or you will switch it on ... and promptly switch it off. The repeat send on the remote control is very fast - check it by holding down GUIDE and see how fast it cycles.
I hope these issues will be fixed by a Humax software update in the future ...