I have had a DMA2100 media center extender for a couple of months now.
After configuring the extender and connecting it the the PC the first time, I was not able to get the PC to sleep again.
I figured out that by changing a setting in power options allowing the computer to sleep during media sharing re-enabled the possibility of getting the PC to sleep.
The next problem that occurred was that the extender was not able to wake up the PC.
I found a solution to that problem, which I will try to describe here. It is not the best solution to the problem, but it works for me and maybe someone else could find it useful.
I installed an additional network adapter in my PC.
I connected th extender directly to the onboard network adapter (using a crossover cable) and enabled wake-on-link, i.e. whenever the link LED on the back of the extender turns on, the PC wakes up.
/Peter