Symptoms
The smart form is asking for user name and password , when I enter the user name and password and close the browser it's prompting again .
Diagnoses
The issue is related to using Forms Authentication instead of Windows. Windows is able to pass the current credentials into the browser to automatically authorize the user.
Resolution
http://help.k2.com/onlinehelp/k2smartforms/userguide/1.0.7/default.htm_authentication.html
Customer switched to Windows authentication and this resolved the issue