Using Ajax to call asp.net web service

Using Ajax to call asp.net web service

I am trying to use an ajax to call a web service written in asp.net.  In Firefox I get the "failure" alert.  In ie 7 I get a javascript error that says "access denied" and no alert is displayed.  I'm very new to this and would like to know how to approach it.

Here is the code I am using:
var fileName = "TheTestFile.xml";
var parameters = "{'XMLToSave':'" + "<root>something</root>" + "','FileName':'" + fileName + "'}";

   $.ajax({
   type: "POST",
   url: 'http://156.114.75.32:8000/savefile/Service.asmx/SaveFile',
   data: parameters,
   contentType: "text/xml",
   dataType: "xml",
   success: function(msg) {
   alert("success");
   },
   error: function(e) {
   // $(divToBeWorkedOn).html("Unavailable");
   alert("failure");
   }
   });

and on the server:

[WebService(Namespace = "http://tempuri.org/")]
[WebServiceBinding(ConformsTo = WsiProfiles.BasicProfile1_1)]
// To allow this Web Service to be called from script, using ASP.NET AJAX, uncomment the following line. 
// [System.Web.Script.Services.ScriptService]
public class Service : System.Web.Services.WebService
{
    public Service () {
        //Uncomment the following line if using designed components 
        //InitializeComponent(); 
    }

    [WebMethod]
    public void SaveString(string XMLToSave, string FileName)
    {
        string dir = @"C:\Inetpub\wwwroot\savefile\testfiles";
        string File = dir + @"\" + FileName;
        StreamWriter sw = new StreamWriter(File);
        sw.Write(XMLToSave);
        sw.Close();
    }
}

Thank you very much.
Jeff