I am trying to use the WebClient on Windows 7/IE9 to SharePoint 2010 which is secured by client certificates. I hope this is the best place as it seems to be a browser/os issue as Windows XP/IE7 works just fine. The issue is when a client attempts to open a SharePoint Library in Explorer View, the user is prompted for their certificate and then prompted for their user id and password twice before failing. As this is going through TMG 2010, I can see a 443 request when the certificate gets requested, but after the cert is selected, TMG throws a response stating a client certificate is required. Therefore, it looks like a certificate is not being sent when using IE9. I have tried various things including add the site to a Local Intranet zone, updating the Web Client\Parameters registry setting for AuthForwardServerList, etc... I guess I am missing some sort of setting as I am unable to make any difference in the responses from the server. Any help would be appreciated! Mark

Hi, Please check if the following articles are helpful. Prompt for Credentials When Accessing FQDN Sites From a Windows Vista or Windows 7 Computer http://support.microsoft.com/kb/943280/en-us Windows 7 Prompting for Authentication When Accessing SharePoint Documents http://www.quantumofgeek.com/2010/02/windows-7-prompting-for-authentication-when-accessing-sharepoint-documents/ Meanwhile, I recommend to post in SharePoint forum to get more insights. http://social.technet.microsoft.com/Forums/en-US/category/sharepoint/ Niki TechNet Subscriber Support If you are TechNet Subscription user and have any feedback on our support quality, please send your feedback here Niki Han TechNet Community Support

Hi, Any udpate on this issue? Niki TechNet Subscriber Support If you are TechNet Subscription user and have any feedback on our support quality, please send your feedback here.Niki Han TechNet Community Support

Hi, As this thread has been quiet for a while, I assume the issue has been resolved. At this time, we will mark it as "Answered" as the previous steps should be helpful for many similar scenarios. If the issue still persists, please feel free to reply this post directly so we will be notified to follow it up. You can also choose to unmark the answer as you wish. BTW, we'd love to hear your feedback about the solution. By sharing your experience you can help other community members facing similar problems. Thanks for your understanding and efforts. Niki TechNet Subscriber Support If you are TechNet Subscription user and have any feedback on our support quality, please send your feedbackhere.Niki Han TechNet Community Support