5.2-RELEASE: unable to mount cd-roms

I am unable to mount CD-ROMs with 5.2-RELEASE.  I get the following 
error message:

cd9660: /dev/acd0: Input/output error

I first noticed this problem when a 5.2-RELEASE miniinst disc would not 
use itself as installation media (I was forced to use FTP instead, even 
though the drive had booted the disc into the installer fine).  I have 
only been able to mount a CD-ROM if the disc is already in the drive 
before booting the computer.  Subsequent attempts fail with the above 
message.  Attempting to mount with "-v" does not provide any further 
info.  Also, toggling "hw.ata.atapi_dma" does not change the behavior.

The drive is installed as the master on ata0.

The full dmesg:
http://www.noacks.org/freebsd/dmesg.20040113.txt

$ grep acd0: dmesg.20040113.txt
acd0: FAILURE - MODE_SENSE_BIG status=51<READY,DSC,ERROR> 
sensekey=ABORTED COMMAND error=4<ABORTED>
acd0: FAILURE - MODE_SENSE_BIG status=51<READY,DSC,ERROR> 
sensekey=ABORTED COMMAND error=4<ABORTED>
acd0: <CREATIVEDVD-ROM DVD2240E 03/18/98/1.8A> DVDROM drive at ata0 as 
master
acd0: read 16007KB/s (32015KB/s), 2KB buffer, WDMA2
acd0: Reads: CDR, CDRW, CDDA, DVDROM, packet
acd0: Writes:
acd0: Audio: play, 65280 volume levels
acd0: Mechanism: ejectable tray, unlocked
acd0: Medium: CD-ROM 120mm photo disc
acd0: WARNING - READ_BIG UDMA ICRC error (retrying request)
acd0: FAILURE - READ_BIG status=51<READY,DSC,ERROR> sensekey=ILLEGAL 
REQUEST error=0

Jon Noack