This problem has mystified me for months. Seemingly at random, my MCE remote will just not wake up my Windows 7 HTPC. The receiver is clearly powered, because the red LED lights up when I hit the power button, but the machine just doesn't wake up. But if I go over and hit the keyboard or click a mouse button, the computer will wake up just fine. But other times (it's about 50/50 whether it will work or not), the remote wakes the computer just fine.
Has anyone ever seen something like this? Any ideas where to start tracking it down?