Hm. When I connect that 3V rail and the board is working again (regardless of whether I have the 5v rail connected, then this chip on the BlueGiga board gets quite hot.

This occurs without any of the I2S pins connected. All that's connected are jumper wires from the Ardunio on these pins:
- 5v (either connected or not)
- 3v
- Gnd
- RX
- TX

This worries me. What has gone wrong with my BlueGiga board I wonder?

And I wonder if that chip or any of its supporting circuitry is the problem and if I can disable it easily?