Logic stores the information of the indexed loops in a database file (LoopsDatabaseV09.db). Maybe your database file is corrupted.
- Quit Logic
- Go to the user directory ~Music/Audio Music Apps/ Databases/
- delete the file LoopsDatabaseV09.db and the Tags folder
- Launch Logic open the Loop Browser and reindex
- Cross your fingers.

You can have the Finder window open and while you are reindexing you can see how Logic rebuilds that database file.
Hope that helps
EdgarRothermich - LogicProGEM.com
(Author of the "Graphically Enhanced Manuals")
http://DingDingMusic.com/Manuals/
'I may receive some form of compensation, financial or otherwise, from my recommendation or link.'