[dexter1]

If i would guess looking at the mainboard configuration of the IP6, could there be debris on the board close to the network controller (SEEQ?) and AUI connector? This could cause shorts between the HPC1.5 and the network controller, rendering connection/loopback tests invalid.

So make sure you eyeloop the affected part of the mainboard.

Also multimeter all the tracks to see if there is a short or broken pad somewhere