I was able to boot ubuntu 12.04 using unknown's kernel and the new u-boot, no errors upon start up, hopefully it stays that way.

attached is item file I used..

some notes:

ITEM_DEVICE="${EXT_CARD}p1"
ITEM_FSTYPE="vfat"

refer to where the uImage is stored rather than where the root device is.

ITEM_KERNEL="uImage"

refer to the uImage name on the first partition of the sdcard, no need to copy the uImage to /boot for regenerating the boot menu.

ITEM_USEATAG=1 is used instead of ITEM_REUSEATAG=1, the system won't boot using the later.(this happens even when booting maemo with kp if ITEM_REUSEATAG=1 is used in KP item file)

remove the .txt extension from the file, copy it to /etc/bootmenu.d/

then run u-boot-update-bootmenu