Thanks for the feedback, everyone. Not trying to mess with the tv settings, just want the panel/box to do its job. Oh well, I'll see how the next hotel goes tomorrow.

In case you're curious, here's part of the press release from 2007(!) regarding the panels:

Washington, DC - 26 February 2007 -

Marriott Hotels & Resorts, JW Marriott Hotels & Resorts, and Renaissance Hotels & Resorts will become the first lodging brands to offer high-definition, LCD televisions with a digital connectivity panel in all its guest rooms in the U.S. and Canada. Using the new plug-in panel, guests can connect a host of digital devices to view on the flat panel, high-definition screen, including laptops, camcorders, digital cameras, video games and more. The standard 32 inch televisions are also equipped with a 25-watt stereo speaker system so guests can listen to the tunes on their MP3 players and iPods; no headphones required.