It might be that your winsock is corupted you might have to reinstall tcp/ip, go to network in control panel, remove all protocols but leave your modem installed, dont remove the adapter. restart and reconfigure, but before you do that try to go to 64.58.76.176 if that brings up yahoo then you have a problem with your DNS, and you will have to specify the DNS for your DailUp.
PS In the words of Kevin Spacy "I RULE"!!!