Can you tell us what kind of network card you are using? Also if you are using WPA or some other kind of connection encryption.
It would also be useful if you could give us some idea of what is working, if anything.
From a command prompt, run these commands
Code:
ifconfig -a
route -n
ping www.google.com
You will have to press Control and C to stop the ping once it starts giving some kind of answer. Copy and paste them here and it will show us how things are set up just now and give us an idea of what needs doing next.
Let us know how you get on,
Chris...