This issue can occur if you are having problems with your ISP account authentication. Your password is not being recognized as a valid password. Verify that the CAPS LOCK key on your keyboard is not altering the case of your password.
Most passwords are case sensitive.
Verify that your Dial-Up Networking connection does not contain incorrect logon information. Double-click the connection to your ISP, and then verify that your user name and password are correct. Close the Dial-Up Networking folder. Try to connect to your ISP, and enter your user name and password when you are prompted to do so. Contact your ISP and verify that they have not disabled your account, changed your password, or are having problems with their account authentication process.