When connecting my "Early 2008" Mac Pro to my new Denon 3808ci AVR, I can only get interlaced output for most resolutions from the Mac's nVidia 8800 GT graphics card. I have posted this issue on the AVR forum here:
http://www.avsforum.com/avs-vb/showthread.php?p=13165042#post13165042
and also on Apple's forum here:
http://discussions.apple.com/thread.jspa?threadID=1404562&tstart=0

Connecting the Mac directly to my projector results in normal operation. Any help appreciated.