Same problem here.  
- Ubuntu 8.04
- DVD -- Plextor PX-716AL

The following snippet recurs in my dmesg output: 

hda: command error: status=0x51 { DriveReady SeekComplete Error }
hda: command error: error=0x54 { AbortedCommand LastFailedSense=0x05 }
ide: failed opcode was: unknown
ATAPI device hda:
  Error: Illegal request -- (Sense key=0x05)
  Read of scrambled sector without authentication -- (asc=0x6f, ascq=0x03)
  The failed "Read 10" packet command was: 
  "28 00 00 10 0b 7c 00 00 02 00 00 00 00 00 00 00 "
end_request: I/O error, dev hda, sector 4206064
------------------

lspci output:

00:00.0 Host bridge: nVidia Corporation C55 Host Bridge (rev a2)
00:00.1 RAM memory: nVidia Corporation C55 Memory Controller (rev a1)
00:00.2 RAM memory: nVidia Corporation C55 Memory Controller (rev a1)
00:00.3 RAM memory: nVidia Corporation C55 Memory Controller (rev a1)
00:00.4 RAM memory: nVidia Corporation C55 Memory Controller (rev a1)
00:00.5 RAM memory: nVidia Corporation C55 Memory Controller (rev a2)
00:00.6 RAM memory: nVidia Corporation C55 Memory Controller (rev a1)
00:00.7 RAM memory: nVidia Corporation C55 Memory Controller (rev a1)
00:01.0 RAM memory: nVidia Corporation C55 Memory Controller (rev a1)
00:01.1 RAM memory: nVidia Corporation C55 Memory Controller (rev a1)
00:01.2 RAM memory: nVidia Corporation C55 Memory Controller (rev a1)
00:01.3 RAM memory: nVidia Corporation C55 Memory Controller (rev a1)
00:01.4 RAM memory: nVidia Corporation C55 Memory Controller (rev a1)
00:01.5 RAM memory: nVidia Corporation C55 Memory Controller (rev a1)
00:01.6 RAM memory: nVidia Corporation C55 Memory Controller (rev a1)
00:02.0 RAM memory: nVidia Corporation C55 Memory Controller (rev a1)
00:02.1 RAM memory: nVidia Corporation C55 Memory Controller (rev a1)
00:02.2 RAM memory: nVidia Corporation C55 Memory Controller (rev a1)
00:03.0 PCI bridge: nVidia Corporation C55 PCI Express bridge (rev a1)
00:06.0 PCI bridge: nVidia Corporation C55 PCI Express bridge (rev a1)
00:07.0 PCI bridge: nVidia Corporation C55 PCI Express bridge (rev a1)
00:09.0 RAM memory: nVidia Corporation MCP55 Memory Controller (rev a1)
00:0a.0 ISA bridge: nVidia Corporation MCP55 LPC Bridge (rev a2)
00:0a.1 SMBus: nVidia Corporation MCP55 SMBus (rev a2)
00:0b.0 USB Controller: nVidia Corporation MCP55 USB Controller (rev a1)
00:0b.1 USB Controller: nVidia Corporation MCP55 USB Controller (rev a2)
00:0d.0 IDE interface: nVidia Corporation MCP55 IDE (rev a1)
00:0e.0 IDE interface: nVidia Corporation MCP55 SATA Controller (rev a2)
00:0e.1 IDE interface: nVidia Corporation MCP55 SATA Controller (rev a2)
00:0e.2 IDE interface: nVidia Corporation MCP55 SATA Controller (rev a2)
00:0f.0 PCI bridge: nVidia Corporation MCP55 PCI bridge (rev a2)
00:11.0 Bridge: nVidia Corporation MCP55 Ethernet (rev a2)
00:12.0 Bridge: nVidia Corporation MCP55 Ethernet (rev a2)
00:13.0 PCI bridge: nVidia Corporation MCP55 PCI Express bridge (rev a2)
00:14.0 PCI bridge: nVidia Corporation MCP55 PCI Express bridge (rev a2)
00:15.0 PCI bridge: nVidia Corporation MCP55 PCI Express bridge (rev a2)
00:16.0 PCI bridge: nVidia Corporation MCP55 PCI Express bridge (rev a2)
00:17.0 PCI bridge: nVidia Corporation MCP55 PCI Express bridge (rev a2)
00:18.0 PCI bridge: nVidia Corporation MCP55 PCI Express bridge (rev a2)
01:00.0 VGA compatible controller: nVidia Corporation GeForce 8800 GT (rev a2)
04:06.0 Ethernet controller: Linksys Gigabit Network Adapter (rev 10)
04:07.0 Multimedia audio controller: C-Media Electronics Inc CM8738 (rev 10)