I just went through this with my DTVPal when I hooked it back up. Denons and Marantz are a little weird. While you may have it set to auto in the receiver settings, you still need to hit the movie mode on the remote. If the signal is broadcast in 5.1, it will switch to surround and you should not need to do the setting again.
Please use the report post button to alert staff to problematic posts. Never quote or respond to them yourself.
Oppo UDP-203 -> Yamaha CX-A5100 -> Sony XBR-75X940C; Mediabridge 6' and 15' HDMI cables.