Airport

[Iceman]

Hi all i seem to have problems with my airport on my macbook. For some reason it seems to connect to my wireless network but wont go on the internet and when i type in the router ip it doesn't connect just keeps sort of searching for the address. Im pretty much a novice when it comes to macs so any help would be great.
Is there anyway to totally wipe all settings and start again or something?
The netbook seems to connect.

Thanks.