I have two WD Elements 2TB externals hooked up to the WDTV Live Hub. I needed to change the directory structure on the drives to be more compatible with the Hub. I did this via my home network using my laptop because the Hub and the external drives connected to it are on my network. Everything was working fine until two movie files were randomly deleted! I was cutting and pasting movies and moving them out of folders. I got to “Back To The Future Part II” without any problems. However, when I cut and pasted the files in the “Back To The Future Part II” folder, an error message popped up telling me that I needed permission and that the the movie file was no longer available!!! At first I thought it was a fluke or an error on my part, but after it happened a second time I stopped. The two movie files are nowhere to be found!
try connecting the hard drive to your laptop and checking its recycle bin, maybe you did more cutting than pasting 
you wouldnt be the first and wont be the last
I connected the external HD to the laptop and the two movies were still there. When I plugged it back into the Hub after clearing the media library the movies showed up. PHEW!
Now, to figure out why the Hub is not seeing all the movies on the HD…
