For what it's worth, every so often I'll make a complete backup of my data and wipe my various NAS & USB disks and then move the data back.
What I'm noticing on firmware 1.08 is some of my files are no longer usable. When Windows comes along to move the file, the source file from the NAS is no longer readable or transferable, and Explorer gives an access denied message. I can, however, *delete* said file.
Granted I'm talking about maybe 1 in every 5000 files is doing this, the rate is much higher than .. well .. zero.

I've noticed this behavior with .mp3, .m4a, and .jpg files so far.
When I come along to another file I'll FTP into it and see if I can't get the file and see if it is usable.