thanks for that mate.
some #### is repeatedly clicking on my google adwords, i recieved a fraud alert with that ip address.
You can ban that IP from accessing your site using your server's control panel. But the person could simply shut down their modem for a little while and restart it to get a new address assigned to them.
Best thing I can suggest is check out the Google adsense forums, to see what others have done in similar situations. Good luck.