I experienced the same problem under 10.04, 10.10, and 11.04 (current system).  I found a reference to a Plextor firmware update, installed it and now problem is solved!  Suggest you and others investigate how to do this update.  It will fix several brands but not all.  I did it quickly, and so fast, I cannot remember how.  Here's the udev output.  Maybe that will help:

kent@kent05:~$ udevadm monitor -e --udev
monitor will print the received events for:
UDEV - the event which udev sends out after rule processing

^Ckent@kent05:~$ 
kent@kent05:~$ 
kent@kent05:~$ udevadm monitor -e --udev
monitor will print the received events for:
UDEV - the event which udev sends out after rule processing

^G
UDEV  [1305927994.644044] change   /devices/pci0000:00/0000:00:14.1/host0/target0:0:0/0:0:0:0/block/sr0 (block)
UDEV_LOG=3
ACTION=change
DEVPATH=/devices/pci0000:00/0000:00:14.1/host0/target0:0:0/0:0:0:0/block/sr0
SUBSYSTEM=block
DISK_MEDIA_CHANGE=1
DEVNAME=/dev/sr0
DEVTYPE=disk
SEQNUM=1850
ID_CDROM=1
ID_CDROM_CD=1
ID_CDROM_DVD=1
ID_CDROM_MRW=1
ID_CDROM_MRW_W=1
ID_CDROM_MEDIA=1
ID_CDROM_MEDIA_CD=1
ID_CDROM_MEDIA_SESSION_COUNT=1
ID_CDROM_MEDIA_TRACK_COUNT=1
ID_CDROM_MEDIA_TRACK_COUNT_DATA=1
ID_ATA=1
ID_TYPE=cd
ID_BUS=ata
ID_MODEL=SAMSUNG_DVD-ROM_SD-616E
ID_MODEL_ENC=SAMSUNG\x20DVD-ROM\x20SD-616E\x20\x20\x20\x20\x20\x20\x20\x20\x20\x20\x20\x20\x20\x20\x20\x20\x20
ID_REVISION=F501
ID_SERIAL=SAMSUNG_DVD-ROM_SD-616E
ID_PATH=pci-0000:00:14.1-scsi-0:0:0:0
ID_FS_VERSION=Joliet\x20Extension
ID_FS_LABEL=microlife_bpa313
ID_FS_LABEL_ENC=microlife\x20bpa313
ID_FS_TYPE=iso9660
ID_FS_USAGE=filesystem
GENERATED=1
UDISKS_PRESENTATION_NOPOLICY=0
MAJOR=11
MINOR=0
DEVLINKS=/dev/scd0 /dev/disk/by-id/ata-SAMSUNG_DVD-ROM_SD-616E /dev/disk/by-path/pci-0000:00:14.1-scsi-0:0:0:0 /dev/disk/by-label/microlife\x20bpa313 /dev/cdrom /dev/dvd
TAGS=:udev-acl:

UDEV  [1305927994.933613] add      /module/isofs (module)
UDEV_LOG=3
ACTION=add
DEVPATH=/module/isofs
SUBSYSTEM=module
SEQNUM=1852

UDEV  [1305927994.935483] add      /kernel/slab/isofs_inode_cache (slab)
UDEV_LOG=3
ACTION=add
DEVPATH=/kernel/slab/isofs_inode_cache
SUBSYSTEM=slab
SEQNUM=1853

UDEV  [1305927995.058497] add      /module/nls_utf8 (module)
UDEV_LOG=3
ACTION=add
DEVPATH=/module/nls_utf8
SUBSYSTEM=module
SEQNUM=1854

UDEV  [1305927995.080261] change   /devices/pci0000:00/0000:00:14.1/host0/target0:0:0/0:0:0:0/block/sr0 (block)
UDEV_LOG=3
ACTION=change
DEVPATH=/devices/pci0000:00/0000:00:14.1/host0/target0:0:0/0:0:0:0/block/sr0
SUBSYSTEM=block
DISK_MEDIA_CHANGE=1
DEVNAME=/dev/sr0
DEVTYPE=disk
SEQNUM=1851
ID_CDROM=1
ID_CDROM_CD=1
ID_CDROM_DVD=1
ID_CDROM_MRW=1
ID_CDROM_MRW_W=1
ID_CDROM_MEDIA=1
ID_CDROM_MEDIA_CD=1
ID_CDROM_MEDIA_SESSION_COUNT=1
ID_CDROM_MEDIA_TRACK_COUNT=1
ID_CDROM_MEDIA_TRACK_COUNT_DATA=1
ID_ATA=1
ID_TYPE=cd
ID_BUS=ata
ID_MODEL=SAMSUNG_DVD-ROM_SD-616E
ID_MODEL_ENC=SAMSUNG\x20DVD-ROM\x20SD-616E\x20\x20\x20\x20\x20\x20\x20\x20\x20\x20\x20\x20\x20\x20\x20\x20\x20
ID_REVISION=F501
ID_SERIAL=SAMSUNG_DVD-ROM_SD-616E
ID_PATH=pci-0000:00:14.1-scsi-0:0:0:0
ID_FS_VERSION=Joliet\x20Extension
ID_FS_LABEL=microlife_bpa313
ID_FS_LABEL_ENC=microlife\x20bpa313
ID_FS_TYPE=iso9660
ID_FS_USAGE=filesystem
GENERATED=1
UDISKS_PRESENTATION_NOPOLICY=0
MAJOR=11
MINOR=0
DEVLINKS=/dev/scd0 /dev/disk/by-id/ata-SAMSUNG_DVD-ROM_SD-616E /dev/disk/by-path/pci-0000:00:14.1-scsi-0:0:0:0 /dev/disk/by-label/microlife\x20bpa313 /dev/cdrom /dev/dvd
TAGS=:udev-acl:

UDEV  [1305928197.241578] change   /devices/pci0000:00/0000:00:14.1/host0/target0:0:0/0:0:0:0/block/sr0 (block)
UDEV_LOG=3
ACTION=change
DEVPATH=/devices/pci0000:00/0000:00:14.1/host0/target0:0:0/0:0:0:0/block/sr0
SUBSYSTEM=block
DISK_MEDIA_CHANGE=1
DEVNAME=/dev/sr0
DEVTYPE=disk
SEQNUM=1855
ID_CDROM=1
ID_CDROM_CD=1
ID_CDROM_DVD=1
ID_ATA=1
ID_TYPE=cd
ID_BUS=ata
ID_MODEL=SAMSUNG_DVD-ROM_SD-616E
ID_MODEL_ENC=SAMSUNG\x20DVD-ROM\x20SD-616E\x20\x20\x20\x20\x20\x20\x20\x20\x20\x20\x20\x20\x20\x20\x20\x20\x20
ID_REVISION=F501
ID_SERIAL=SAMSUNG_DVD-ROM_SD-616E
ID_PATH=pci-0000:00:14.1-scsi-0:0:0:0
GENERATED=1
UDISKS_PRESENTATION_NOPOLICY=0
MAJOR=11
MINOR=0
DEVLINKS=/dev/scd0 /dev/disk/by-id/ata-SAMSUNG_DVD-ROM_SD-616E /dev/disk/by-path/pci-0000:00:14.1-scsi-0:0:0:0 /dev/cdrom /dev/dvd
TAGS=:udev-acl: