Ubuntu has more trouble reading DVDs than Fedora on same hardware

I've noticed a couple of weird bugs with the DVD-ROM on my laptop in Ubuntu that
aren't a problem in Fedora Core 3.

1. DVD's that I burn on my Plextor (I've used 3 different types of media, DVD-R
4x, DVD-R 8x, and DVD+RW 4x), sometimes, and unpredictably, are unreadable on my
laptop in Ubuntu, but not Fedora. Here are some of the different kinds of
behaviors I've seen:

- Inability to detect a filesystem on the DVD using both "udf,iso9660" and
"auto" in /etc/fstab:

12:05% mount /media/cdrom
mount: wrong fs type, bad option, bad superblock on /dev/hdc,
       missing codepage or other error
       In some cases useful info is found in syslog - try
       dmesg | tail or so

from dmesg, nothing but:
UDF-fs: No VRS found
Unable to identify CD-ROM format.

- Weird iso9660 errors when I try to force the filesystem type to iso9660. After
a successful:
> sudo mount -o ro -t iso9660 /dev/hdc /media/cdrom

ls of /media/cdrom is *empty* and the following messages are in dmesg:

ISO 9660 Extensions: Microsoft Joliet Level 3
Interleaved files not (yet) supported.
File unit size != 0 for ISO file (1792).
ISOFS: changing to secondary root
Interleaved files not (yet) supported.
File unit size != 0 for ISO file (1920).

Note that the above will *usually* happen with some DVD-Rs, and never happen
with others. I haven't been able to pinpoint the problem.

2. Pressed DVD playback on my laptop using xine has "microskips" of a few
frames, sometimes up to a half-second. VOBs on the hard drive don't have this
problem. This happens when the system is plugged in and the CPU speed is pegged
to maximum (1.6 GHz). I'm not sure if this is related to the 1st problem, but I
figured it's useful to mention it.

Details of my setup:

Linux puri.chappati.org 2.6.10-4-686 #1 Tue Feb 22 23:26:31 UTC 2005 i686 GNU/Linux

Matsushita UJDA745 DVD-ROM/CD-RW combo drive, firmware 1.05 (just upgraded, had
problems with older firmware too)
IBM Thinkpad T40p
1.6 GHz Pentium-M (controlled effectively by powernowd)
Triple boot of
 - Windows (haven't tried much but it seems to work with these DVD-Rs fine)
 - Fedora Core 3 (none of these problems), running 2.6.9 and 2.6.10
 - Ubuntu hoary, updated daily, including newest linux-image-686

More details of the hardware of the system can be found by plugging "2373-G3U"
as a model-type code into the "Quick path" field of http://www.pc.ibm.com/support