Simple solution:

To resolve this issue, first locate the Rasphone.pbk file and make sure that the read-only file property in the Properties dialog box is not selected. If it is not selected, the file may be damaged and you must rename the Pbk folder to Pbk.old.

The Pbk folder is located in the "C:\Documents and Settings\All Users\Application Data\Microsoft\Network\Connections" folder. If you cannot see the Pbk folder, make sure that you can see hidden files and folders.

To do so, follow these steps:

1. Click Start , click My Computer, and then click Folder Options on the Tools menu.
2. Click the View tab.
3. Click Show hidden files and folders, and then click OK.