Also to look at, is replacing the front display board (with the front panel LEDS) which affects both the USB and LAN connectivity. I've had to replace a number of these in the past on different XPR8300 repeaters. The USB interface controller resides on this board.
I've never seen Motorola provide a Field Service Bulletin on this issue, although I felt that they should have.
Paul Metzger
K6EH