How-do-I—Stop-the-double-logon-prompt-when-opening-a-document-in-SharePoint-document-libraries
I get this one a LOT in the support forums and the answer is quite simple. I finally got tired to typing out the steps and decided to put together a quick Article for it.
http://www.cjvandyk.com/blog/Articles/How-do-I—Stop-the-double-logon-prompt-when-opening-a-document-in-a-SharePoint-document-library.aspx
Cheers
C