XmlDocument.Save throwing access denied error

Hello all,

I'm trying to append to an existing XML file on a web server running IIS 7 on Windows Server 2008.

I have no problem getting the information added to the file, however when I go to save, I get the asp error: Access to the path '\\servername\drive$\directory\file.xml' is denied.  (obviously, I changed the information to make it general)

I have tried giving the group "Everyone" full control to both the directory and the file itself for testing purposes.  I have also done the same for user IUSR since anoynmous is allowed.  No matter which approach I try, I get the same error.

Here is the code that I'm using in case it helps:

xDoc.Save("//servername/drive$/directory/file.xml");

 I have also tried: xDoc.Save(xDoc.Save(HttpContext.Current.Server.MapPath("file.xml"));

And that gives this error: A ...