Avi files on hard disk is corrupt after transfer

Hi, i hope this post is in the correct place and that the issue haven’t been up before, I cannot find anything similar atleast.

I got 2 external drives, the one is a 500GB MyBook, the other a 1,5TB Elements, both NTFS formatted

I recently transferred a big avi collection from the MyBook to the Elements, and now i cant play some of the movies.

I guess something went wrong when i relocated the files, but i have no idea what ?

Sadly i deleted the files on the old hard disk, so i hope someone knows if i can restore the files.

they are all the correct size and doesnt look corrupted.

im running Lion on a MBP

Just noticed, some of the files is completly mixed up, one file can contain parts of 2 other movies, and some is only half their original time and then switches to another movie etc… im very confused now 

Could it be because you are forcing NTFS file transfer between 2 devices using an operating system that does not natively support that file system? Just to test it out, do you get file corruption as well when you transfer the files from one drive to another using a Windows computer?