Airport problems - Macbook 1g connecting to the network but not the internet

[MacAodh]

Hi all,
Myself and my girlfriend both have 1st generation macbooks, mine with the faster processor. For some reason her's has stopped connecting to the internet. It connects to the network but not beyond. Mine is 100%.

Is there anywhere in particular I should be looking to solve this?

 

[Queso]

Check her System Preferences>>Network>>Advanced panel for the Airport interface. There's a tab marked TCP/IP. Does it have an entry next to the Router field? Also in the DNS tab there should be something in the DNS servers list.