Hi Charles,
Thanks you for your response. I did Like you said, and it worked like a charm :).
But I have always the same problem. In fact, when I write system.img file ( generated by android in yaffs format ) in system partition with write.yaffs uboot command, the command lasts only few seconds and when I boot to Android the partition is mounted but it is empty ( containing lost+found directory ).
I tried also with nand write command and the partition is always empty.
I have no clue about the origin of the problem. Could you help me get through ?
Thank you for your help.