The record is not open

I am sitting with a Windows Server 2008 R2, SQL Server 2008 R2 and installed NAV2009 SP1 Web Services.

Have a different server with Windows Server 2008 and SQL Server 2008.
Same configuration for WS on both servers, it runs on the same service accounts (domain accounts). Both SQL instances also use the same service accounts.

Using a copy of the same db on the 2 servers.

Opening the url: http://servername:port/DynamicsNAV/WS/Services I can see the exposed Web Services.
Opening the url: http://servername:port/DynamicsNAV/WS/companyname/Codeunit/servicename I can see the functions that the Web Service exposes.

The following successfully returns the list of companies:

    MyRef.Url = "http://servername:port/DynamicsNAV/WS/SystemService"
    MyRef.UseDefaultCredentials = True
    companylist = MyRef.Companies()

Upon calling WorldTest (a simple function that returns "Hello World!"), I get the error: "The record is not open"

  Dim WService As New WSRef.WorldService   

  Try
    WService.UseDefaultCredentials = True
    MsgBox(WService.WorldTest())
  Catch ex As Exception
    MsgBox(ex.Message)
  End Try

However on the second server all works fine. I have seen that UAC might cause this issue and turned it off, but no success.

Kind Regards