Hm, one last follow-up.  Now the _1st_ access after a power-cycle + boot
causes a problem.  All subsequent accesses, including those after a
warm reboot, work fine.

This is the error:

cd0(ahc0:0:0): timed out in dataout phase, SCSISIGI == 0x0
cd0(ahc0:0:0): BUS DEVICE RESET message queued.
Bus Device Reset Message Sent
cd0(ahc0:0:0): Bus Device Reset delivered. 1 SCBs aborted

This happens with disklabel -r cd0 and other data accesses,
and also with "cdplay" and "xmcd".

	Sean.