When mine does that, I go to my IP, "Renew IP" and it usually works. If it doesn't, I unplug everything and that usually solves everything, but if it doesn't, it's my cable connection.

 

What Operating system are you on?
Do you have a software firewall?
What is your computer's IP address?
Are you using WEP encryption?
Can you ping the router?
ping 192.168.1.1 (if still using default...)

PM me when you answered these questions, I don't check O-T too often.

-John