169 IP address and authentication server not responding?

I have just started trying to connect to my dad's wireless again. I managed to connect yesterday and this morning, but then it randomly disconnected. The other MacBook in the house is fine. It gives itself an IP address starting with 169, which obviously doesn't work and then when I change it and try to connect it says "Authentication server is not responding". Is there any way I can solve this problem. I am using Snow Leopard.