use kermit upgrade firmware failed

HI all, I am trying to upgrade ATMEL AT91RM9200 board by using Kermit.
From Uboot, I send loadb 20400000, then from kermit send my firmware to this board. But after reboot, it stops at:

/bin/sh: can't access tty; job control turned off
#

if use ps to check Linux process loaded, I get nothing.

But I can use tftp from Uboot load the same firmware to board, run everything successfully.

Below is my screen capture, any help will be appreciated.


Starting kernel ...

Linux version 2.4.27-vrs1 (lewis@lewis-VirtualBox) (gcc version 2.95.3 20010315 (release)) #1 Tue May 29 13:04:57 EST 2012
CPU: Arm920Tid(wb) revision 0
Machine: ATMEL AT91RM9200
On node 0 totalpages: 4096
zone(0): 4096 pages.
zone(1): 0 pages.
zone(2): 0 pages.
Kernel command line: root=/dev/mtdblock2 rootfstype=jffs2 console=ttyS0,115200 mem=16M
Relocating machine vectors to 0xffff0000
Calibrating delay loop... 79.46 BogoMIPS
Memory: 16MB = 16MB total
Memory: 14112KB available (1614K code, 384K data, 60K init)
Dentry cache hash table entries: 2048 (order: 2, 16384 bytes)
Inode cache hash table entries: 1024 (order: 1, 8192 bytes)
Mount cache hash table entries: 512 (order: 0, 4096 bytes)
Buffer cache hash table entries: 1024 (order: 0, 4096 bytes)
Page-cache hash table entries: 4096 (order: 2, 16384 bytes)
CPU: Testing write buffer: pass
POSIX conformance testing by UNIFIX
Linux NET4.0 for Linux 2.4
Based upon Swansea University Computer Society NET3.039
Initializing RT netlink socket
Starting kswapd
devfs: v1.12c (20020818) Richard Gooch (rgooch@atnf.csiro.au)
devfs: boot_options: 0x1
JFFS2 version 2.2. (C) 2001-2003 Red Hat, Inc.
pty: 256 Unix98 ptys configured
USSP driver registered.
RAMDISK driver initialized: 16 RAM disks of 8192K size 1024 blocksize
loop: loaded (max 8 devices)
PPP generic driver version 2.4.2
PPP Deflate Compression module registered
PPP BSD Compression module registered
SCSI subsystem driver Revision: 1.00
i2c-core.o: i2c core module version 2.6.1 (20010830)
i2c-dev.o: i2c /dev entries driver module version 2.6.1 (20010830)
usb.c: registered new driver usbdevfs
usb.c: registered new driver hub
usb.c: registered new driver serial
usbserial.c: USB Serial support registered for Generic
usbserial.c: USB Serial Driver core v1.4
usbserial.c: USB Serial support registered for PL-2303
pl2303.c: Prolific PL2303 USB to serial adaptor driver v0.10
ttyS%d0 at MMIO 0xfefff200 (irq = 1) is a AT91_SERIAL
ttyS%d1 at MMIO 0xfefc4000 (irq = 7) is a AT91_SERIAL
ttyS%d2 at MMIO 0xfefc0000 (irq = 6) is a AT91_SERIAL
ttyS%d3 at MMIO 0xfefc8000 (irq = is a AT91_SERIAL
ttyS%d4 at MMIO 0xfefcc000 (irq = 9) is a AT91_SERIAL
at91_ether: PHY not detected.
AT91 Watchdog Timer enabled (5 seconds)
AT91 Real Time Clock driver
host/usb-ohci.c: USB OHCI at membase 0xc18ef000, IRQ 23
usb.c: new USB bus registered, assigned bus number 1
hub.c: USB hub found
hub.c: 2 ports detected
i2c-dev.o: Registered 'AT91RM9200' as minor 0
Found AT91 i2c
AT91 SPI driver loaded
at91_dataflash: Atmel AT45DB321B detected [spi0] (4325376 bytes)
Creating 3 MTD partitions on "Atmel AT45DB321B":
0x00000000-0x00023100 : "bootloader"
0x00023100-0x000f3600 : "kernel"
0x000f3600-0x00420000 : "filesystem"
NET4: Linux TCP/IP 1.0 for NET4.0
IP Protocols: ICMP, UDP, TCP
IP: routing cache hash table of 512 buckets, 4Kbytes
TCP: Hash tables configured (established 1024 bind 1024)
ip_conntrack version 2.1 (128 buckets, 1024 max) - 308 bytes per conntrack
ip_tables: (C) 2000-2002 Netfilter core team
NET4: Unix domain sockets 1.0/SMP for Linux NET4.0.
NetWinder Floating Point Emulator V0.97 (double precision)
jffs2: Erase block size too small (0KiB). Using virtual blocks size (2KiB) instead
VFS: Mouit memory (jffs2 filesystem).
Mounted devfs on /dev
Freeing init memory: 60K


BusyBox v1.00 (2012.05.29-03:04+0000) Built-in shell (ash)
Enter 'help' for a list of built-in commands.

/bin/sh: can't access tty; job control turned off
/ #

My very first guess would be that your image uses too much space, doesn't uboot have to know both start and end adress?