You guys crack me up with some of your suggestions!
Do the usual turn it off and on again, should sort it. No need to reset the router or anything. Will be an idea to reboot the laptop when you're done too, just to clear out any settings it might have temporarily saved stopping it from seeing the network. Vista is a bit pants when it comes to networks, but a quick reboot normally does the trick even when Diagnose and Repair doesnt work