What I did to resolve the issue for myself was to check for any black stars in the album rating. I generally don't use this field myself, so there weren't a lot that I had to fix.
Last Christmastime I created a smart Playlist called Favourite Albums for all tracks where the album rating (grey) was 5 stars. I had manually set some albums to 3 or 4 stars in order to exclude incomplete albums. When I later added the remaining songs from those albums, they inherited the album ratings for the songs, thus screwing up my song rating-based playlists. I had also added a few new favourite albums in the meantime and shortcutted the process by rating the albums 5 stars.
I had to go back over all songs added over the last year and remove the manual album ratings where appropriate. Curiously, you can't do it in song view, but only in album view, so there was a lot of back and forth between the two views.
I can't remove them all or my Favourite Albums playlist will be messed up. I will have to be vigilant whenever I add tracks to check for manual album ratings that need to be cleared. As it sits today, they only exist for incomplete albums.
I wish iTunes had a value for album is complete/incomplete that could be used for smart playlists.
I would also like a "play only when shuffling" option for various comedy albums to intersperse with my music.