I've used this on my old, non-HD setup a year or two ago. I just assembled a new HT system:

Sony KDF-50E3000 50" LCD projection HD TV
Marantz SR-4001 A/V receiver
Sony generic DVD player
Comcast A-S 4250HDC cable box.

The cable box connects to the Marantz w/HDMI input. The Marantz then connects HDMI output to the TV HDMI input.

I'm trying to program the Harmony550 and cannot figure out the settings.
I first setup all the devices listed above.
Then I started setting up activities and it gave me a message that there were no video switching devices. Apparently it didn't recognize that the Marantz AVR provided a HDMI video connection to the TV !

Also, when I looked at the TV settings, It listed a bunch of video inputs but listed no HDMI.

Am I missing something here?

Thanks,
Rob