I have noticed that the component and S-Video (and presumably other "SD") outputs have different color balances. Specifically it seems like the component outputs are over-driven compared to my other sources. The S-video output matches pretty closely what the built in cable TV tuner in my TV was producing. The component output is much brighter and more saturated (note, this is not a good thing, even though it might sound like it). My solution is to just recalibrate the component input on my TV to match, but I suppose Dish could fix that with software if they so chose.
I wouldn't expect tech support to know anything about such issues. Without knowing the internal design of the 921, as well as parts of the software, you can only guess at what's actually going on. I also doubt that a new 921 would change that issue.
As for the "black&white only" problem, that sounds like there might be a lose connection in the s-video cable or connector. S-Video cables carry 2 signals, the Y and the C (which is a combination of the Cb and Cr found in component). The Y signal is the luminance, or black/white signal, and the C is (you guessed it) the color information. If there was some problem with the C signal then you'd end up with exactly what you described. This *might* be defective hardware (connector, especially), so a replacement *might* fix it.
On the other hand, since other people have reported the problem appearing with the L211 software, or go away with a reboot, I'd have to also suspect software. If some piece of software is mis-programing a video chip such that the C signal is "lost" to the great bit-bucket in the sky, then you would also get that effect. It's a somewhat sad statement that it's even possible to have such a bug, as properly designed software would (as a side effect) ensure that either all the signal gets there, or none of it does (in case of a logic or hardware error). Partial failures tend to indicate that there are more failure points than there should be. (It can also indicate that the software realized a specific error had occurred, and tried to give as good of result as possible, but I somehow doubt that's the case).
-- Dave