The request failed with HTTP status 401: Unauthorized

It's along story, but I will try make it as short as I can.
RS is installed on the same server with the WebServer. I run this from a
domain network PC:
http://WebServerName/Reports/Pages/Folder.aspx
and I receive this error:
The request failed with HTTP status 401: Unauthorized.
What I checked:
1.On the WebServer go in IIS , then Default Web Site, then Reports, then
Proprieties, then Security and ONLY Integrated Windows Authentication is
checked
2. The save as above for ReportService under Default Web Site
3. Open Windows Explorer on the Web Server and go to C:\Program
Files\Microsoft SQL Server\MSSQL\Reporting Services\ReportServer where
ReportService.asmx file is located. In the same folder have a look in
web.config file and:
    <authentication mode="Windows" />
    <identity impersonate="false" />
4 IIS is version 6
5. Web Server is Windows 2003
6. Bellow is a copy of the RS log file where the error is logged:
w3wp!ui!1860!17/02/2006-13:20:44:: e ERROR: The request failed with HTTP
status 401: Unauthorized.
w3wp!ui!1acc!17/02/2006-13:20:44:: e ERROR: The request failed with HTTP
status 401: Unauthorized.
w3wp!ui!1acc!17/02/2006-13:20:45:: e ERROR: HTTP status code --> 500
-------Details--------
System.Net.WebException: The request failed with HTTP status 401:
Unauthorized.

   at
System.Web.Services.Protocols.SoapHttpClientProtocol.ReadResponse(SoapClientMessage message, WebResponse response, Stream responseStream, Boolean asyncCall)

   at System.Web.Services.Protocols.SoapHttpClientProtocol.Invoke(String
methodName, Object[] parameters)

   at
Microsoft.SqlServer.ReportingServices.ReportingService.ListSecureMethods()

   at Microsoft.SqlServer.ReportingServices.RSConnection.GetSecureMethods()

   at Microsoft.ReportingServices.UI.RSWebServiceWrapper.GetSecureMethods()

   at
Microsoft.SqlServer.ReportingServices.RSConnection.IsSecureMethod(String
methodname)

   at Microsoft.ReportingServices.UI.Global.SecureAllAPI()

   at
Microsoft.ReportingServices.UI.ReportingPage.EnsureHttpsLevel(HttpsLevel
level)

   at Microsoft.ReportingServices.UI.ReportingPage.ReportingPage_Init(Object
sender, EventArgs args)

   at System.EventHandler.Invoke(Object sender, EventArgs e)

   at System.Web.UI.Control.OnInit(EventArgs e)

   at System.Web.UI.Control.InitRecursive(Control namingContainer)

   at System.Web.UI.Page.ProcessRequestMain()
w3wp!ui!1860!17/02/2006-13:20:45:: e ERROR: HTTP status code --> 500
-------Details--------



Could anyone give help?