Onkyo TX-SR606 and Xbox 360 HDMI issues

Hi guys. I've been trying to figure this one out for ages, but to no avail.

I have an Onkyo TX-SR606. I have a PS3 and Xbox 360 connected via HDMI, a digital optical from a mac mini input and then HDMI to my TV.

The only source I have problems with is the Xbox 360. After about 2-5 minutes of having the console on, the receiver will start flashing the HDMI light and the TV will flicker on and off with signal.

I've switched HDMI ports, changed HDMI cables, checked settings on both the Onkyo and the Xbox, but still getting it almost every time I boot it up.

It's hard to explain really well what happens, so I recorded it and threw it up on Youtube. If you just want to see it in action, skip to 2:30.



Any ideas how to stop this?

Ah yes, one additional point. When I plug the 360 directly into the TV, I don't get the issue. My initial thought is that it's the HDCP handshake between the receiver and the xbox, but it doesn't make sense as to when it happens.