Access DLookup produces runtime error 2471

Hi,
this routine fails with runtime error 2471.  What might be wrong?
Thanks,
Brooks

Private Sub Print_Label_Click()
    Dim strPartNumber As String
    Dim strExists As Integer
    strPartNumber = Me.cboPN
    ' This section sees if part number is axial leaded or chip
    ' See if the diode part number exists in the diodes table
    ' If it is an axial leaded part use Glassing Furnace Diode Label
    ' If it is a chip use Glassing Furnace Chip Label
    strExists = DCount("[P_Number]", "Diodes", "[P_Number] = strPartNumber")
    If strExists <> 0 Then
    Stop
        DoCmd.OpenReport "Glassing Furnace Diode Label", acViewNormal, , "[ID]=" & Me.ID
    Else
    Stop
        DoCmd.OpenReport "Glassing Furnace Chip Label", acViewNormal, , "[ID]=" & Me.ID
    End If
   
End Sub