Internet Connection died - Airport still active


I'm running os x 10.4.2 on a 15" powerbook g4.

My internet has always just worked. When I turned the computer on for the first time, it automatically jumped on my wireless network. That was 2 months ago. Today, for the first time, it stopped working. I'm still connected to my wireless network, but my router won't assign it an IP address. I tried connecting the laptop directly to my cable modem, but that wouldn't even work. My dad's 12" iBook still has connectivity, as does the PC that I'm on right now (PC is hardwired to network). I've restarted the computer multiple times, turned airport off/on etc, tried manually inputting IP/DNS settings, but to no avail.

I'm at a complete loss. I have no idea what caused this. Does anyone have any ideas? Thanks for your time.