Can't create or write to a file w/ASP.NET: UnauthorizedAccessException

I have a C# ASP.NET 2.0 application that needs to write some simple logging records to an XML file in the bin directory under the www root.  If I attempt to create or write to the file, I get an UnauthorizedAccessException.  (Access to the path 'D:\webadmin\www\bin\test.xml' is denied).  My server administrator says the ASP.NET user has write access to the bin directory, and I'm not sure what else the problem could be.

My testing code...  this code is compiled code-behind in the bin directory (same directory I'm trying to write to) and the ASPX page is up one directory (under the root).


filepath = @"D:\webadmin\www\bin\test.xml"
if (!File.Exists(filepath)) {
      File.Create(filepath); //Error is thrown here.
}