I was able to boot it using the boot settings suggested for NITdroid.
ITEM_NAME="Ubuntu 9.10 Karmic (external SD, partition 2)" ITEM_ID="ubuntu" ITEM_DEVICE="${EXT_CARD}p2" ITEM_MODULES="mbcache jbd ext3" ITEM_FSTYPE="ext3" ITEM_FSOPTIONS="noatime,rw"