[U-Boot] copy to flash: Flash not Erased

Hi,

I have some problems with using u-boot writing to flash: ( arm 920 processor )

first I use tftp to download the kernel to memory and was successful:

tftp 0x800000 mImage OK

then I try to erase part of the flash, seems ok:

erase 0x1c040000 0x1c8FFFFF erased 124 sectors

then I use cp.b command, failed with the "Flash not Erased" message cp.b ${fileaddr} 0x1c040000 ${filesize}

copy to Flash...-Flash not Erased.

and no detailed error message was given.

any idea what could be wrong ?

Thanks for the help in advance.

Howard