Thank you Mike for your helpful reply, and sorry for my negative comment.
I had already wound back the firmware, twice, as some files I still can’t get to play, though they play fine on a USB stick plugged into WDTV (that’s in another thread, http://community.wd.com/t5/WD-TV-Live-Streaming/NAS-Problem-solved-by-factory-reset-but/m-p/794115#M33131). I had marked it as solved, re the GUI but the file playback problem is still bugging me. Perhaps I should put that into a new thread, since the old one is “solved”?
I will go away and try your other suggestions and report back. Thanks again. I hate networking, always have!
