Win7 64-bit and Sqlite3 database.
Had a folder named "Namc YS11". Shift + F5 to rename in the location tree. Rename to "NAMC YS11" and bye bye to thumbnails in the folder. So, it appears TP9 does not like when you simply change the case of part of the folder name. UGH.
The above action from the thumbnail list (F2 to rename folder) does not remove the folder thumbnails. However, the name is not refreshed in the location tree.