Also, not sure if this helps, on particles. When you download the cover art and then go to Theater View, the Cover shows correctly, but when you put the mouse over the cover the info panel first shows the cover then switches to the thumbnail of the last particle cover art downloaded. But then, this is more interesting, if you then Erase all thumbnails and restart the program, all the cover art images are now gone in Theater view and are replaced with the last thumbnail image.
So the cover art was changed to thumbnails after the Erase all thumbnails action.