I have the latest firmware on mine and it kept working with my receiver, I am using optical audio. It is weird that rolling back the firmware fixed the audio issue, and you might want to email western digital or search around the WD community
if you haven't already. So with the new firmware, it only works when you connect it directly to your tv? Is there light coming out of the optical audio jack in the back?
I think the problem may be that the meta data downloads automatically for files only on a connected usb drive It doesn't search for files on the SMB share, but I heard WD is working on that in a future firmware release. It takes your filename and searches it on thetvdb.com. It then generates an xml file. I have all my files in mkv. I have one movie in ISO format and the metadata downloaded correctly for it, too.
It downloads box art, actors, director, rating, genre, pictures, year, description, etc. from thetvdb.com. The way my setup works, when I get a movie or tv show rip and copy it to the wdtv (I have the hub version), it automatically gets metadata.
However, there is a tool available here
where you can get metadata and put it into a format that wdtv recognizes. It should work when it sees those files on your smb share.