Reboot the router! It isn't yours, is that problem? It looks as though we cannot help, as ever bit of help we give you, you will not be able to perform. Go and talk with the person to which you are "borrowing" their bandwidth!
Perhaps the person has not paid the internet bill! They still have a router to connect the wifi, but their service has been turned off due to non payment! Perhaps you should talk with them and see if you can't help them out with turning it back on!