wireless problem

I'll try to keep it short. I have a wireless router on the main pc, and an adapter on the other pc. Both the same make (lynksys). They worked fine for some time. Then suddenly the remote machine couldn't connect, and gave a message that the IP address was invalid. It displatyed all zeros. I used the "setup" buttons (their term) on the router to try establish a new connection, and the adapter gave a new ssid and whatnot, but then the remote machine still couldn't connect. Now the remote machine can't even find the network. The remote adapter seems to work, since it can still find other networks, and the router still seems to work and has lights on and whatnot. I know this is a bit murky and I'm not using the proper terms.

What is the likely source of this problem? Does it sound like something I can fix or is some part of the router just dead? I don't want to go buy another if I can avoid it. I tried searching and it's hard to tell what the problem is, given the sequence of problems. I don't want to make matters worse. All help appreciated.