When I tried renaming a few pictures, the thumbnails changed and wont show the picture anymore. Instead, the thumbnail now is a black square, with the word EXEC in the top left corner written in green. When I open the file, it still opens fine in preview, but the thumbnail doesn't work. I tried changing the files to jpegs and bmps, but that wont work either. And then some others are just blank white icons, but they still open fine in Preview as well. Any help is appreciated, thanks!!!