usb flashkey disk copy error

Hello all,

I have a copy error between hdd and a flashkey 1gig usb (easydisk)
on Current dated August 28. Here is in short:

mount -t msdos /dev/da2s1 /flashkey
cp myfile /flashkey/
diff myfile /flashkey/myfile
	(ok).
umount /flashkey

mount (flashkey)
diff myfile /flashkey/myfile
	(Binary file differ)!

It is not a flashkey disk error, it works on XP.
Note that this error occurs on FreeBSD 4.8 too.

Please, can you tell me how to deal with that?
And in an other hand can you tell me how to obtain the exact map of the flashkey
to verify the writing on the disk.
Thanks in advance for this newbie question.

raoul.megelasz_at_libertysurf.fr