Kernel panic - not syncing: Attempted to kill init!

[myuboot@fastmail.fm]

Hi, 

I got the following error trying to bring up the /sbin/init with Kernel
2.6.31 using cramfs filesystem on a MIPS 32 board:

[    1.160000] VFS: Mounted root (cramfs filesystem) readonly on device
31:2.
[    1.171000] Freeing unused kernel memory: 116k freed
[    1.223000] Kernel panic - not syncing: Attempted to kill init!
[    1.229000] Rebooting in 3 seconds..

Using BDI I know the kernel panic happens as soon as
run_init_process("/sbin/init") in init_post() is called. The filesystem
itself seems to be ok, because I can use 'ls' command under u-boot to
see /sbin/init is a symbolic link to busybox. Also the kernel seems to
like the filesystem and can mount the filesystem.  I have for checked
for similar questions for this error, so I tried replacing /sbin/init
with a hello world program, but the result is exactly the same. It seems
neither hello-world or /sbin/init got executed. 

At this point, I don't know how to debug this issue. Any suggestion on
how to debug this issue will be greatly appreciated.

Andrew