self-assigned IP doesn't work!

My brand-new Macbook worked fine on my boyfriend's wireless network, but as soon as I got it home, it no longer wanted to actually connect to the internet. The Airport extreme card keeps assigning itself an IP, like it's unable to get one from the router. I tried giving it a static IP which didn't work either.

Please oh please help me out! AppleCare just had me on hold for 2 hours.