A Very Strange Network Problem

Hi all. I'm new to the board and new to MACs and I need your help!

Here's the setup

I've got a 2.16, 15in MacBook Pro that I have previously used to connect wirelessly in my home office. No problems occured until I updated OSX with the security upgrades this past week. Airport detects and says it's connected to my home router but Safari says it's not connected to the internet.

Network diagnostics says Airport, Airport Settings, and Networksettings check out but that ISP, Internet, and Server have failed.

DCHP is set to automatic, I've performed router (Linksys Wireless-G running 128bit security) and modem restarts (Motorola Surfboard), still nothing.

However, if I restart the computer it can connect wirelessly to my network again. The Mac will also connect to other wireless network in the area without fail. It works when hardwired in as well. I've looked through the router settings and I can't figure out what could be causing this. Can anyone help me?

 

More Info

Network status says Airport is connected by does not have an IP address and cannot connect to the internet.

Could this be a router based problem?