No, I have not. Although, I use it all the time to watch movies on my Mac. So the device itself has no difficulties with streaming large files for playback.
do you have it connected directly to the USB port or networked somehow?
the reason I ask is that I have had some funky results tranferring large files (or several smaller ones) via the network.
often times when I transfer, for example, an album of mp3 tracks, four or five files (from 12-15) simply get dropped. no warnings or errors, they just aren't there.
so perhaps we are having a network problem and not a WD harddrive problem.