After running the "Build missing thumbnails" on a Media Server client, the thumbnails are still not built. I tried erasing and re-building all thumbnails on the client, and even though it took almost an hour and a half and said it was done, I can still see MC building the thumbnails when I first browse to an album on the client. Also, as I navigate, only the first line of the album art appears until I scroll the track pane, after which the remaining lines of the album art appear.
This didn't happen a couple builds ago -- i.e. once I ran the "re-build" function, the thumbnails all showed up immediately as I navigated.
Larry
PS. Please see my posts above for other "image" related bugs, such as the fact that Audible files are not displaying any art in MC12 (these files DID display art in MC11.)