SCSI CD mount problems

I have a Yamaha CRW4416S CD drive as /dev/cd0.  When I try to mount a disk,
it says "cd9660: /dev/cd0: Invalid argument", and this in the log file:

(cd0:ahc0:0:3:0): READ(10). CDB: 28 0 0 0 0 10 0 0 1 0 
(cd0:ahc0:0:3:0): CAM Status: SCSI Status Error
(cd0:ahc0:0:3:0): SCSI Status: Check Condition
(cd0:ahc0:0:3:0): ILLEGAL REQUEST asc:21,0
(cd0:ahc0:0:3:0): Logical block address out of range
(cd0:ahc0:0:3:0): Unretryable error
(cd0:ahc0:0:3:0): cddone: got error 0x16 back


I know the drive works, I can write good disks with it.  What's happening
here?  This is on 5.1-RELEASE.

 -Guy