A MacFixIt reader reports an odd bug in iTunes where album groupings are being split up after batch editing data, similar to when album names are slightly different.
"An easy fix is to do a batch get-info, and under "Options" call the group a "Compilation". This forces the songs to appear in a group, the way you would expect an album of songs to look. I discovered that if you subsequently do ANOTHER get-info and DESELECT the Compilation option, the songs will still remain together."There are other reasons why your album may not be grouped properly. Even if the words are identical in the album name, an additional character (such as a space) is read as a different album name. To find out more, read this Apple KB article.