Prompted for credentials when using Open with Explorer in SharePoint 2010

Hello,

When using "Open with explorer" in libraries, I get prompted for credentials. The site is a trusted site with IE.  I am using Windows 8.1 with IE 11, and SharePoint 2010. The site is set as local intranet and in security settings for local intranet the User Authentication is set to "automatic logon only in intranet zone". Changing to "Automatic Logon with current user name and password" has no effect. I also have alternative access mappings for the site set in SharePoint with FQDN, http://server.domain.com, and users access the site with the same URL.  Plus, the "web client" service is running on the client.  

Any suggestions on what to do to stop the prompts for passwords?

Thanks

Paul