Ubuntu 10.04 preseed unattended install results in faulty partition table

I'm currently trying to set up an unattended installation of Ubuntu 10.04 (Lucid Lynx) through preseeding. But whenever I try to create a custom partition scheme, the Debian installer (which Ubuntu is using) produces a faulty partition table.

I've taken the partition scheme described in the example preseed file:

d-i partman-auto/expert_recipe string                         \
      boot-root ::                                            \
              40 50 100 ext3                                  \
                      $primary{ } $bootable{ }                \
                      method{ format } format{ }              \
                      use_filesystem{ } filesystem{ ext3 }    \
                      mountpoint{ /boot }                     \
              .                                               \
              500 10000 1000000000 ext3                       \
                      method{ format } format{ }              \
                      use_filesystem{ } filesystem{ ext3 }    \
                      mountpoint{ / }                         \
              .                                               \
              64 512 300% linux-swap                          \
                      method{ swap } format{ }                \
              .

Unfortunately it also produces an incorrect partition table on the disk. The installation process itself is working and the installed system eventually boots and is working, as far as I can tell. But fdisk and cfdisk are still complaining:

# fdisk -l /dev/sda

Disk /dev/sda: 17.2 GB, 17179869184 bytes
255 heads, 63 sectors/track, 2088 cylinders
Units = cylinders of 16065 * 512 = 8225280 bytes
Sector size (logical/physical): 512 bytes / 512 bytes
I/O size (minimum/optimal): 512 bytes / 512 bytes
Disk identifier: 0x000a1cdd

   Device Boot      Start         End      Blocks   Id  System
/dev/sda1   *           1           5       37888   83  Linux
Partition 1 does not end on cylinder boundary.
/dev/sda2               5        2089    16736257    5  Extended
/dev/sda5               5        2013    16121856   83  Linux
/dev/sda6            2013        2089      613376   82  Linux swap / Solaris

cfdisk even refuses to start at all:

# cfdisk /dev/sda

FATAL ERROR: Bad primary partition 1: Partition ends in the final partial cylinder

parted on the other hand does not complain about the cylinder boundary of /dev/sda1:

# parted /dev/sda p
Model: VMware Virtual disk (scsi)
Disk /dev/sda: 17.2GB
Sector size (logical/physical): 512B/512B
Partition Table: msdos

Number  Start   End     Size    Type      File system     Flags
 1      1049kB  39.8MB  38.8MB  primary   ext4            boot
 2      40.9MB  17.2GB  17.1GB  extended
 5      40.9MB  16.5GB  16.5GB  logical   ext4
 6      16.6GB  17.2GB  628MB   logical   linux-swap(v1)

Since the installed system is working, it shouldn't be a big problem but I'm afraid that this will mean trouble in the future.

It's probably a bug in the Debian installer of Ubuntu 10.04 since the version provided for Karmic Koala is working as expected and creates a correct partition table. I've filed a bug report on Launchpad on this issue.