Users are Prompted for Credentials Multiple Times When Adding the Web Interface for SharePoint Web Part to an Existing SharePoint Site.

Symptoms

Users are prompted for credentials multiple times when adding the Web Interface for SharePoint Web Part to an existing SharePoint site. Accessing a SharePoint site with an included Web Interface for SharePoint Web Part also displays this behavior.

Cause

This problem occurs if the SharePoint portal site Security Configuration is set up to use Kerberos authentication. With the introduction of SharePoint Portal Server Service Pack 2, the default Security Configuration for SharePoint sites is Kerberos. The configurable account for Kerberos is to use a domain account and Web Interface for SharePoint is set up to use the Network Service. Because you can only have one Service Principal Name (SPN) per application, you must change the identity of the Web Interface for SharePoint service provider to be the same as the rest of the portal server.

Resolution 1

Open the IIS Admin tool on the SharePoint server.
Expand the Internet Information Services (IIS) site where Web Interface for SharePoint is installed.
Right-click the Web Interface for SharePoint Web application and go to Properties > Directory
Change the Application Pool associated with the /_layouts/WISP/ Web application to be the same as the /_layouts/ Web application.

Resolution 2

Open the IIS Admin tool on the SharePoint server.
Expand the Application Pools node and locate the WispAppPool
Right-click the WispAppPool and go to Properties > Identity
Change the identity from a Network Service to a domain account.

More Information

CTX108349 – Web Interface for Microsoft SharePoint Administrator's Guide