After you install SP2, Microsoft ActiveSync 4.0 no longer works with a Widcomm Bluetooth stack.
This behavior occurs because Windows XP SP2 automatically installs its own device driver during a slipstreamed upgrade, overwriting the existing 3rd party Bluetooth adapter driver.
NOTE: If you install SP2 (not slipstreamed) when a 3rd party Bluetooth adapter driver is already installed, it does NOT overwrite the driver.
When you try to install the 3rd party driver, you can't, because the Windows XP driver is ranked higher in Plug and Play because it is signed.
NOTE: The Bluetooth discovery and pairing works with the Widcomm stack, but ActiveSync does not offer to synchronize with the desktop when the COM port settings remain the same.