Can't boot with zImage.img but vmlinux

Hi

I have problems with booting uClinux (NOMMU) on DE0 Board.

I can't successfully boot uClinux kernel with zImage.

But I can boot uClinux kernel with vmlinux.

My u-boot version is u-boot-2011-06.

The build of the kernel from nios2-linux-20110603 seems to work

When I download the "zImage" to my SDRAM and try to use the bootm command to boot uClinux.

But after a while only show the below message and then nothing happens

--- Quote Start ---

==> fatload mmc_spi 0 01C00000 zimage.img

reading zimage.img

1457659 bytes read

==> bootm 01C00000# # Booting kernel from Legacy Image at 01c00000 ...

Image Name: linux- 2.6

Image Type: NIOS II Linux Kernel Image (uncompressed)

Data Size: 1457595 Bytes = 1.4 MiB

Load Address: 01804000

Entry Point: 01804000

Verifying Checksum ... OK

Loading Kernel Image ...

OK

OK

--- Quote End ---

this is my borad information

--- Quote Start ---

==> bdinfo

mem start = 0x01800000

mem size = 0x00800000

flash start = 0x82400000

flash size = 0x00400000

flash offset= 0x00000019

ethaddr = (not set)

ip_addr = 0.0.0.0

baudrate = 1 bps

--- Quote End ---

I create zImage.img by mkimage tool. The following information is setting of zImage.image

--- Quote Start ---

mkimage -n 'linux- 2.6' -A nios2 -O linux -T kernel -C none -a 0x01804000 -e 0x01804000 -d zImage zImage.img

--- Quote End ---

PS. The success of booting kernel that I use "go" command + vmlinux.bin rather than "bootm" command + zImage.img

Thank you for your help!!!!!!!!!!!!!!!!!!!!!!!