Okay, my setup looks like this:
Macbook Pro 17" mid 2009 mini-DVI port to hdmi converter to hdmi cable to Marantz SR-5004. HDMI to Pioneer KRP-500M.
When I try to use the tv as an external monitor (vids played on the mac), I get a "no signal" message on the tv. I have hooked up the same exact cables directly from Macbook Pro to Pioneer, no change. I connected the same cables from my Macbook to a friends tv and also to the backup Samsung tv downstairs. Displays fine on both. On the Macbook, it doesn't even show as a recognized external display the Pioneer. PS3 and Directtv work just fine running thru Marantz to Pioneer and using their hdmi cable to my macbook doesn't solve the issue (it can't be the Marantz).
Many people on the apple forums have had an issue with their video output, but I don't. My only problem seems to be with the Pioneer. Anyone heard of an issue like this or know of something I can do to fix the tv? Thanks guys!