I know that when I plug my 3G iPod into my PowerBook and tell it to sleep, it keeps charging...
if that doesn't work, you still have your wall socket, right?
Well.. since the computer is technically still on (just.. paused?) I don't see why the power would be cut off...
Could you try a factory reset and see if that helps?
And I bet you've done this, but make sure it's plugged in really well.