There are still some handshake issues with HDMI.
Your better bet is to go with the component cables, but if you insist on HDMI, then I suggest you search for the tv receiver's compatibility with the Samsung.
I purchased a LN46A650 in late June and hooked it up to a new Scientific Atlanta RNG200 box from Comcast via HDMI at HDMI 1. The Comcast box is outputting at 1080i.
I also connected a Sony DAV-HDX275 DVD Changer/Audio systems through an HDMI cable (at HDMI 2) and ran the digital audio out from the TV to the Sony.
For 3+ weeks it worked perfectly.
Last week I added a Wii through component video 1 (not sure if this is related). Several days later, when switching back to HDMI 1 for TV (and when the Comcast RNG200 box was still outputting at 1080i), I began getting a "Mode Not Supported" message from the TV. There are no problems with the DVD player though.
I've updated the firmware on the TV and trawled the internet but didn't really see any answers that worked for me (I've tried resetting, changing cables out, etc.). While I can work around this issue by running the cable box to the TV via component video/audio, I'd like to get the HDMI working again.
Any thoughts would be much appreciated!