2014-04-26, 04:09
My guess is that the database (Textures13.db) had rows claiming the artwork was present in the cache, but the files didn't actually exist in the Thumbnails folder, so XBMC had nothing to display as it wouldn't have found any of the cached files. XBMC should have complained about this in the log, though as you have worked out, deleting Textures13.db or running C fixes the problem and gets your XBMC back in sync.
A more optimal solution is to use the "X"/"Xd" options: "X" will list any rows from Textures13.db that reference non-existent Thumbnails files, while "Xd" will delete these rows.
A more optimal solution is to use the "X"/"Xd" options: "X" will list any rows from Textures13.db that reference non-existent Thumbnails files, while "Xd" will delete these rows.