Right, I can see your images now.
It looks like you are using the WD desktop application to copy files to the drive. Have you tried mapping the drive into windows file system (see p23 of the manual), and using windows file explorer to access the drive?
Can you access the Dashboard?
Can you still watch movies using your AppleTV?
Given that it stalls after so few bytes have been transferred, I suspect your firmware has recently automatically upgraded, and this has damaged the share permissions (although I would have hoped the all would have given a suitable error message about permissions). See the following thread for a firmware patch that might fix your problem:
