Does anyone have experience with an LC475 and MacCon ethernet boards?

I have dusted off an old LC 475, and although it boots nicely, it is in 
slight disagreement with the Ethernet card it has on board. This is part 
of my dmesg:

ae0: at nubus0 slot e: MacCon LC III, 32 KB memory
ae0: Ethernet address 00: (etc etc)
ae0: length does not match next packet pointer
ae0: len 0000 nlen ff00 start 0c first 00 curr 36 next 00 stop 80
ae0: NIC memory corrupt - invalid packet length 65280

Since this board works like a charm from the Mac OS, and its identical 
twin does exactly the same, I assume there's a driver that needs a little 
tweek. Anyone got any suggestions?

-John