1. Have you tried it both with and without that null modem adapter?

2. Are you plugging the earthmate directly into the player's serial port, or are you using a docking sled? Remember that those two methods are opposite in terms of crossover. depending on the earthmate's wiring, you'd need the straight-through cable for one of them, and the null adapter for the other.

3. If you're using a docking sled, have you ensured that you're using only pins 2, 3, and 5 on the serial connector, and that the other pins are disconnected?

4. How is the earthmate getting its power?