I've noticed an annoying problem with my Samsung LNT375HA. Its a 37" 720p, hooked up to an upconverting Pioneer dvd player.
Whenever I switch inputs away from the dvd player (to see the score of the game or something), I lose the picture on the hdmi input until I turn off the TV and turn it back on again. The sound is still there, but the TV no longer recognizes there is any input.
Anyone have any idea if that's just a quirk of hdmi, or something peculiar to my TV?

Welcome to the pain in the ass problems with HDMI (thank-you MPAA).

1) Try a different cable.

2) See if there is a firmware update for your TV.

3) See if your cable box is outputting 1080i (sometimes a setting in the menus) and see if you can change it.

It could be a quirk of your particular TV/DVD combination. Make sure they both have the latest firmware. See the following post on HDMI issues (quite common).

http://www.digitalhome.ca/forum/showthread.php?t=71112