3500AG read problems

Hello, all!
I’m having the next problem -
I’m trying to read dvd-rw disk written with LG usb dvd-rw recorder.
Disk contains 6 rar archives.
All archives turn out to be corrupted when I copy them to hard drive. Files are copied OK - no crc errors or anything.
Anytime I calculate md5 hash value of those archives directly from my nec - I get DIFFERENT values. This basically means that everytime when I read from my dvd-rw I get some number of wrong bytes…