I got it working. I need to execute "make distclean". In the attachement is the u-boot.kwb which is working on my sheevaplug. Your kernel will be deleted if you flash your plug with the u-boot.kwb:
Marvell>> reset
resetting ...
U-Boot 2009.08-rc1-00039-gb30fcb0 (Aug 26 2009 - 07:59:58)
Marvell-Sheevaplug
SoC: Kirkwood 88F6281_A0
DRAM: 512 MB
NAND: 512 MiB
Net: egiga0
88E1116 Initialized on egiga0
Hit any key to stop autoboot: 0
NAND read: device 0 offset 0x100000, size 0x300000
NAND read from offset 100000 failed 0
3145728 bytes read: ERROR
(Re)start USB...
USB: Register 10011 NbrPorts 1
USB EHCI 1.00
scanning bus for devices... 1 USB Device(s) found
scanning bus for storage devices... 0 Storage Device(s) found
Wrong Image Format for bootm command
ERROR: can't get kernel image!
Marvell>>