Apparently this is what the 360 does as I have the exact same problem and I also use the cable trick. Kreeee told me it was a flaw in the design.
Mine resets if the game hasnt 'started'
What is this trick?
Cunning. Pretty tight/clever of MS to put the ports so close together that you can't do this without paying ££ for their cable or hacking cables apart!
I have the Elite and use the official hdmi cable and audio adaptor too connect it too surround sound and can switch between my pc and xbox 360 (both connected via hdmi) and it doesnt reset the 360 just get a pop up box saying HDCP connection established
It has 2 connectors 1 hdmi and 1 audio adaptor block which has rca and optical audio connectors on it which connects it too my surround sound system