Rename machine using WMI in VB.Net

I am looking to call WMI to do a rename and join workgroup.  The following
functions compile cleanly but the renale doesn't seem to work:

Function objGetComputerSystem() As ManagementObject
        Dim objectQuery As New ObjectQuery("select * from
Win32_ComputerSystem")
        Dim searcher As New ManagementObjectSearcher(objectQuery)
        Dim computerSystem As ManagementObject
        Dim computerSystemOut As ManagementObject
        computerSystemOut = Nothing
        For Each computerSystem In searcher.Get()
            computerSystemOut = computerSystem
            Exit For
        Next computerSystem
        Return computerSystemOut
    End Function

    Function renameComputer(ByRef computerSystem As ManagementObject, ByVal
newName As String) As UInt32
        Dim rc As UInt32

        Dim objArgs(1) As Object
        objArgs(0) = newName
        rc = computerSystem.InvokeMethod("Rename", objArgs)
        Return rc

    End Function

    Function JoinWorkgroup(ByRef computerSystem As ManagementObject, ByVal
newWorkgroup As String) As UInt32
        Dim rc As UInt32

        Dim objArgs(5) As Object
        objArgs(0) = newWorkgroup
        objArgs(1) = vbNull
        objArgs(2) = vbNull
        objArgs(3) = vbNull
        objArgs(4) = vbNull


        rc = computerSystem.InvokeMethod("JoinDomainOrWorkgroup", objArgs)
        Return rc

    End Function

The objGetComputerSystem  works but the rename silenlly fails.  I havent
cheched the JoinWorkgroup function yet.  Any Ideas?