If the WMP library works the same as in XP/Vista, it'll be as follows:
- Edit album artist
- WMP writes album artist to its own library
- WMP periodically writes data in library to the actual file's metadata
It's step 3 that always fails for me. Which would mean that the file's metadata wouldn't ever get up to date, which would mean that the Libraries wouldn't be able to pivot on that data. The only way of fixing it that I see is getting Windows Media Player fixed, but I'm sort of giving up on that, since nobody else seems to have this problem.