type in flasher-3.5 -F <firmware-image> --flash-only=kernel -f -R into maemo flasher but you have to have the maemo firmware image in the flasher and the n900 connected and everything. i had the same error when i installed nitdroid and the maemo power kernel at the same time. i still dont know what the cause was and also flashing the kernel will erase multiboot. im not sure what itll do to meego, but maemo will stay the same.
flasher-3.5 -k zImage -l --boot="init=/sbin/preinit_orig ubi.mtd=rootfs root=ubi0:rootfs rootfstype=ubifs rootflags=bulk_read,no_chk_data_crc rw console=ttyMTD,log console=tty0 snd-soc-rx51.hp_lim=42 snd-soc-tlv320aic3x.hp_dac_lim=6"