This happen to some people when the DSL provider changes your IP address your modem picks up the new address but your router doesn't. When you turn the router off and on it request the IP address from the modem and apply the new setting. I have to do this all the time when my connection slows down to a halt. I have cable internet though, same thing happens because they change your address constantly to prevent you from hosting a server. They want you to paid extra for static IP.