wtf?

[quangntenemy@localhost mandriva]$ md5sum xaa
28cac97e24514e00da387d605d64e9d4  xaa
[quangntenemy@localhost mandriva]$ cp xaa /home/quangntenemy/iso/
[quangntenemy@localhost mandriva]$ md5sum /home/quangntenemy/iso/xaa
30b5260aa446ba28e9aa5cc2d31f3766  /home/quangntenemy/iso/xaa
[quangntenemy@localhost mandriva]$ cp xaa /home/quangntenemy/iso/
cp: overwrite `/home/quangntenemy/iso/xaa'? y
[quangntenemy@localhost mandriva]$ md5sum /home/quangntenemy/iso/xaa
8bf1672d80eef1beefcc528ea8bff1ba  /home/quangntenemy/iso/xaa
[quangntenemy@localhost mandriva]$ cp -f xaa /home/quangntenemy/iso/
[quangntenemy@localhost mandriva]$ md5sum /home/quangntenemy/iso/xaa
26c5636cb00f103689f9432e9ff529a8  /home/quangntenemy/iso/xaa
[quangntenemy@localhost mandriva]$ md5sum /home/quangntenemy/iso/xaa
26c5636cb00f103689f9432e9ff529a8  /home/quangntenemy/iso/xaa
[quangntenemy@localhost mandriva]$ f***
bash: f***: command not found
[quangntenemy@localhost mandriva]$ cp xaa /mnt/data/iso/
[quangntenemy@localhost mandriva]$ md5sum /mnt/data/iso/xaa
28cac97e24514e00da387d605d64e9d4  /mnt/data/iso/xaa

Err wtf's happening here?

I was trying to copy a file of about 2GB from my USB to my hard disk, but the checksum failed all the time :(

In the end I managed to get things done by copying the file to a fat32 partition instead.

I guess it's kinda buggy copying files between different types of partition...

Any explanation?