partman-auto creates faulty partition table on netboot with preseed

Binary package hint: debian-installer

I'm trying to set up an unattended installation of Ubuntu 10.04 with the netboot kernel (http://archive.ubuntu.com/ubuntu/dists/lucid/main/installer-amd64/current/images/netboot/ubuntu-installer/amd64/). When using a custom partition scheme, the Debian installer or more precisely partman-auto always produces a faulty partition table.

Besides several custom partition schemes I've tried out the partition scheme described in the example preseed file (https://help.ubuntu.com/9.10/installation-guide/example-preseed.txt):

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)

This problem only occurs during a netboot installation with the kernel and initrd of Ubuntu 10.04. When using the one provided for Ubuntu 9.10 (http://archive.ubuntu.com/ubuntu/dists/karmic/main/installer-amd64/current/images/netboot/ubuntu-installer/amd64/) everything works as expected and a correct partition table is generated during the installation.