bluetooth license check failed (?)

I have a Vostro 1500 (with 355 bluetooth module) running XP Pro SP3. Recently I got this error message, entitled Bluetooth Software License:

Bluetooth license check failed. Please make sure that the Bluetooth device is plugged in/turned on, the device you are using is licensed for this software and that your license has not expired.

Needless to say, the bluetooth system stopped working. I reinstalled the bluetooth drivers and everything went back to normal, but after a little while the same message popped up again. I downloaded the most current bluetooth software from Dell, with the same result. I'd be grateful for any ideas about what to do next.

Many thanks for all suggestions,

Mark