Had the same problem from time to time. I don't know why it doesn't plug and play but rebooting finally reconizes it. PIA isn't it?
Recently, I moved house and went from a cable internet system to a land line with a wireless sender. This was the start of my problems. Firstly, I lost connectivity, but in fact losing is the wrong word. I actually gained an extra network provider. Anyway I saw the forum on "removing Plug'n Play" and this problem seems to have stopped. What I am left with is the same thing with printers and now, finally the keyboard. Eventually after several reboots, disconnections etc, it solves itself.
However, I can't believe that this is not in some way connected to the Wireless Network problem. Any readers give me some detailed help.