[Yaffs] lost all file

I had port yaffs to my embed board(with a 512M nand flash and ucos system ) for a few months. It work well mostly.

But for a few times, I lost all files in yaffs2 after a reboot, nothing left event in lost and found.
It seem to be a totally new disk partation.
    This problem didn't happend frequently, and I can't find a method to debug or hunt it
down.
    Any one konw what would case this happend? And ,what can I do to trace this problem?
    Any suggest whould be appreciate!    

　　　　　　　　Vinge.Ven
　　　　　　　　winglion1@163.com
　　　　　　　　　　2010-01-13