We call this a "connect can't browse"
Top 3 solutions: (for a dial-up connection)
1. Assuming you're using Internet Explorer: clear cache: Tools>Internet Options>click on Delete Files, check "Delete all offline content", click OK.
2. Also in Int. Options, go to "Connections" click "LAN settings", ensure nothing is checked off unless your ISP has told you to set a proxy server. (Uncheck "Automatically Detect Settings")
3. With your Windows CD handy, go to Control Panel, Add-Remove Programs, Windows Setup, uncheck COmmunications, click OK, wait, ignore prompt for reboot, click Add-Remove Programs again and add the check back to Communications, OK, reboot. You'll have to recreate your dialup connection properties in DialUp Networking. Make sure you know the DNS number of your ISP.
Willie-O (Tech Support never gets a real day off)