CAUSE
This behavior can occur if any of the following conditions are true:
1. The settings for your dial-up connection to your ISP are configured incorrectly.
2. The dial-up connection's security option is incorrectly configured to use the Require secured password setting.
3. Your ISP's Point-to-Point Protocol (PPP) server is not functioning properly.
4. You type an incorrect user name or password.
Verify Your User Name and Password
1. Make sure that the CAPS LOCK key has not been accidentally pressed and engaged.
2. Click Start, point to Connect To, and then click your dial-up connection.
3. In the Connect dialog box, verify that your user name and password are correctly typed in the User name and Password boxes as provided by your ISP, and then click Dial.NOTE: If you are not sure what your user name and password are, contact your ISP for assistance.
Allow Unsecured Password
Configure your dial-up connection to your ISP to allow an unsecured password. To do this, follow these steps:
1. Click Start, click Control Panel, click Network and Internet Connections, and then click Network Connections.
2. Click your dial-up connection, and then click Change settings of this connection under Network Tasks.
3. Click the Security tab, and then verify that Typical (recommended settings) is selected.
4. In the Validate my identity as follows box, verify that Allow unsecured password is selected.
5. Click the Options tab.
6. Click to clear the Include Windows logon domain check box (if it is selected), and then click OK twice.
But Now a days this error can be of the following reason :
BSNL Dial Up Post Paid Connection Error : 691
username = stdcode with phonenumber
ie : 04985 266100
becomes : 4985266100 as username, ie "0" omited
and common password given by BSNL for all users is :
bsnl10
Do it Yourself Plz...
