[kamocat]

Thanks, I forgot to put one on both ends.
I'm using bdc-comm right now, for superstitious aid.
I've tried both 120 ohm and 100 ohm resistors, but no change. I've even measured the resistance between CANL and CANH after assembly, but it's around 50 ohms, just as you'd expect.
I guess the next thing is to take out an O-scope and see if there's any data being sent on the bus at all. There should be a heardbeat from bdc-comm.