Possible Causes :-

1. Dial-in account is not created or suspended --
   1. If you are a new user and are logging on for the first time, probably your dial-in account is either not ready or not created yet. You may need to call your ISP Helpdesk to confirm.
   2. If you are an existing user and you have delayed the payment to your internet subscription, your ISP may choose to suspend your account until you pay up. In this case, you should pay your bills. However, if you have already paid, you should contact the Sales or Billing department to make sure that they have released your account. 
2. Incorrect user name -- 
   1. The user name is your userid that you should only enter them all in lower cases. If your email address is superman@singnet.com.sg, your userid is superman.
   2. Try clearing your user name and re-enter again as there may be some spacing in front or after your user name.
3. Incorrect login password -- 
   1. Make sure you have entered them lower cases with no spacing.
   2. Clear the password and try entering your password again.
4. Wrong dial-in number -- 
   1. Make sure it is the correct  dial-in number as your ISP may have different numbers for different accounts.
5. Corrupted Dial-Up Networking --
   1. Try reinstall Dial-Up Networking as some of its files or configuration may be corrupted. Get your Windows CDROM ready as you may be prompted.
6. Corrupted Dialer -- 
   1. Try creating a new dialer as the existing dialer may be corrupted
7. Data corruption due to incorrect modem driver -- 
   1. Make you have installed the correct driver for your modem.
8. Data corruption due to modem -- 
   1. Your modem may be faulty. Try testing with another modem
9. Data corruption to COM port -- 
   1. Your COM port may be faulty. This is very difficult to test but it is possible. Try lower the maximum speed for the COM port that used by the modem. If you are using an internal or USB modem, this COM port comes with your modem and this may means that your modem is faulty.