Wireless routers, wired routers, cable modems, DSL modems, and all AirPort bases of all types are tiny embedded- OS computers. They are usually very reliable, but they are not built to what you'd call "mission critical" standards-especially their OSs. ANY TIME you have odd behavior on your network it's a great idea to power cycle EVERYTHING. Turn it all off and then restart one piece at a time, beginning with the modem and working toward the computers. This is not a true cure-all, but it is a "cure-99% of all" solution.