CCR1016-12g cannot Boot

Hello,
we buy 5 CCR1016-12g and 2 of them cannot boot after few days.
the message we can seen on the LCD sreen is :

Loading Kernel from nand

the system stay on this position.

when we connect a console cable and boot the router, we have message bellow in the Hyperterminal screen.

please can someone help ?

RouterBOOT booter 3.09
CCR1016-12G
CPU frequency: 1200 MHz
Memory size: 2048 MiB
NAND size: 512 MiB
Press any key within 2 seconds to enter setup..
trying bootp protocol… failed
kernel loading failed
loading kernel from nand… OK
setting up elf image… OK
jumping to kernel code

Hi all,

please can someone help here ???

reinstall ccr with netinstall
http://wiki.mikrotik.com/wiki/Manual:Netinstall

and use latest ROS http://download2.mikrotik.com/routeros/6.6/routeros-tile-6.6.npk

Hi thx,
l did it and it ok now.