HDMI issue between Onkyo 876 and Pioneer KRP500A

[kwangomango]

Hi,

I wondering if anyone could shed some light on the issue i'm having between the Onkyo receiver and the Pioneer plasma.
The Onkyo has two HDMI outputs one of which works perfectly fine. However when i select and connect via the secondary output i get no picture. What is most odd though is that if i try and bring up the menu system on the Pioneer, it appears for a couple of seconds and then closes. After this the Pioneer no longer responds to any remote commands or buttons on the display. The only way to fix it is to reconnect via the other output on the Onkyo or to power down both units.
I've also tried this whilst in Service Menu using ControlCal, but even the Service Menu shuts down just like the regular menu.
What could the Onkyo possibly be doing to cause the plasma to lock up? I have tried two different 876s and both behave the same. I also spoke to Pioneer UK and they have no records of a compatibility issue.
Just for clarification, i have tried numerous sets of HDMI cables and rechecked the settings on both the Onkyo and the Pioneer.
Any ideas?
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Harley-Davidson Model 7 (http://www.cyclechaos.com/wiki/Harley-Davidson_Model_7)

[Turbe]

Have you called to Onkyo's support?

[kwangomango]

Have you called to Onkyo's support?

Yes, i've been talking to the MD of Genserve who deal with Onkyo's European servicing. He was good enough to send me another 876 to test with but this has the same problem. After speaking today he said he would send an email to one of Onkyo's top engineers to see what they had to say about the problem.
I am very curious as to what the 876 could possibly be doing to cause the Pioneer to lock up when i access any of its menus.
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VT750CD (http://www.cyclechaos.com/wiki/Honda_VT750CD)