Thanks for the reply. I've tried creating an .item file at /etc/multiboot.d/ pointing to the uImage at the external SD card. The u-boot updater simply ignores it. Could you please post your .item file here?
ITEM_NAME="Nemo" ITEM_KERNEL="uImage" ITEM_DEVICE="${EXT_CARD}p3" ITEM_FSTYPE="vfat" ITEM_CMDLINE="root=/dev/mmcblk0p1 rootwait ro console=ttyO2,115200n8 console=tty0 omapfb.vram=0:2M,1:2M,2:2M mtdoops.mtddev=2 quiet" ITEM_USEATAG=1