Laptop can access network but IE\FF can't access internet :(?

My friend has a wireless network that I helped setup. One of the laptops about a month ago stopped being able to access the internet using IE and FF (Using Windows XP). Acts as if there is no connection. But it was connected to the network and can access shared drives etc. I couldn't see why, so I decided to disable ZoneAlarm. This worked, so I just enabled Windows Firewall and left it.

Well now it is doing the same thing again. Disabling Windows Firewall did not help. It connects to the network, has an excellent signal, but IE\FF can't access the internet.

An ideas? For now I just recommended they leave the laptop offline until we figure this out.

They mainly just go to MySpace. I didn't see anything in the history to suggest otherwise. Not sure what has happened.

Again, everything was working fine, then it just stopped. Other computers can access the network and use IE\FF just fine.

Thanks