My first bricked XG-100 simply would not talk to the outside world. CH-721 head, it would send power on over the can bus and the brick responded, but no return data on the can bus. I JTAGed the mru and managed to get a recent burnapp and bootapp into the brick.
Still nothing on the RS232 and only one way on the can bus.
Conclusion was a hardware failure in the complex comm's switching to the OMAP. Means a new PK board.