I have notices that when tagging with an editer like musicmatch or the like that sometimes the file does not want to unpack. I have found that removing the art and sometimes doing a bitrate conversion to the same or smaller bitrate seems to make it work more seamless.
All in all I think it is a great program, I might just have to work with it more to pick up on it's mannerisms but still see it as miles ahead of anything elae that I have seen so far