SSRS Web Service LoadReport() Exception Being Thrown

I am getting the following e开发者_高级运维xception when calling the LoadReport() method of the ReportExecutionService2005 web service provided by SSRS 2005;

System.Web.Services.Protocols.SoapException: Server did not recognize the value of HTTP Header SOAPAction

Any ideas what may cause this? My C# code looks like this;

string _reportName = "/FolderName/ReportName";
string _historyID = null;
WebServiceProxy.RSExec.ExecutionInfo _executionInfo = null;

_executionInfo = rsExec.LoadReport(_reportName, _historyID);

All the credentials are set using;

System.Net.CredentialCache.DefaultCredentials;

Turns out I was using the wrong URL for the execution service. For anyone else that stumbles across this problem, make sure you use the right url's!!!!

ReportingService2005 = http://<server name>/ReportServer/ReportService2005.asmx
ReportExecution2005 = http://<server name>/ReportServer/ReportExecution2005.asmx