If something like that happen :

My Acidfree album structure has disappeared: http://ismaili.net/heritage/acidfree-albums Although each image is still there, but albums show as empty. http://ismaili.net/heritage/acidfree-albums/acidfree-albums

Check in the Categories if there is severals Acidfree albums, do the following :

1. Find the id of the vocabulary with terms in it (it should be 2)
2. Activate devel module and activate block devel (be sure you have the good access right)
3. Use Variable editor and edit acidfree_vocab_id and set the vocabulary id you found. Save
4. Deactivate devel module
5. Suppress redundant vocabularies (every Acidfree albums except the one you with the good id)