We are using the following setting to preseed a LVM configuration during netinstaller setup on multiple servers without any issues.
d-i partman-auto/method string lvm
d-i partman-lvm/device_remove_lvm boolean true
d-i partman-lvm/confirm boolean true
d-i partman-auto/expert_recipe string \
boot-root :: \
150 150 150 ext3 \
$primary{ } $bootable{ } \
method{ format } format{ } \
use_filesystem{ } filesystem{ ext3 } \
mountpoint{ /boot } \
. \
5120 5120 5120 ext3 \
$primary{ } method{ format } format{ } \
use_filesystem{ } filesystem{ ext3 } \
mountpoint{ / } \
. \
500 10000 1000000000 ext3 \
method{ format } format{ } $lvmok{ } \
use_filesystem{ } filesystem{ ext3 } \
mountpoint{ /var } \
. \
4096 4096 4096 linux-swap \
method{ swap } format{ } $lvmok { } \
.
d-i partman/confirm_write_new_label boolean true
d-i partman/choose_partition \
select Finish partitioning and write changes to disk
d-i partman/confirm boolean true
This works with the latest Debian 5.0.6. Please try this settings. I you want I could post our whole configuration.