You are prompted unexpectedly to enter your credentials when you access a SharePoint Server site from a Windows Vista-based or Windows Server 2008-based client computer that has a proxy server configured
Consider the following scenario:
- On a Windows Vista-based or Windows Server 2008-based computer, you configure a proxy server in Windows Internet Explorer.
- You use the Web Distributed Authoring and Versioning (WebDav) protocol to access a Microsoft Office SharePoint Server site.
In this scenario, you are prompted unexpectedly to enter your credentials three times. However, you expect that you can access the site directly.
For example, you are prompted to enter your credentials three times when the following conditions are true:
- You open a Microsoft Office file from a SharePoint Server site.
- To open the file, you use a 2007 Microsoft Office system program on a Windows Vista-based client computer that has a proxy server configured.
Note: This problem does not occur on a Windows XP-based computer.
For more information on this issue, including potential causes, workarounds, and resolutions, see: Microsoft KB Article KB956943.