I am running Mandrake 9.1, which should be plenty new enough.

root:/home/arromdee# mount --version
mount: mount-2.11x
root:/home/arromdee# mount -o ro,session=1 -t udf /dev/cdrom /mnt/cdrom
mount: wrong fs type, bad option, bad superblock on /dev/cdrom,
or too many mounted file systems

session=0 does work but only shows some files, which I believe are from the
first session.

A FAQ at http://fy.chalmers.se/~appro/linux/DVD+RW/ says that "DVD+R media
does have notion of multiple sessions. However! DVD-ROM drives can only "see"
the first one. DVD+R burners will be the only ones capable to access the
files added at different occasions." Does this refer to only unfinalized
disks or to finalized disks too? Does it also apply to multisession DVD-R as
well as multisession DVD+R? (Is there even such a thing as multisession
DVD-R?)

The DVD-ROM drive is a Creative DVD6240E (6X).

How can I read the extra sessions on my disks? Do I have any chance other
than buying a new drive? Would buying a new drive actually help?
--
Ken Arromdee / arromdee_AT_rahul.net / http://www.rahul.net/arromdee

"How pleasant it would be if only we lived a hundred years ago when it was
easy to get servants."
"It would be horrible... We'd be the servants." -- Isaac Asimov