Good job with that fix!
Perhaps the thumbnail cache was inconsistent.
On Microsoft Windows operating systems (starting with Windows 2000), a thumbnail cache is used to store thumbnail images for Windows Explorer's thumbnail view. This speeds up the display of images as the smaller images do not need to be recalculated every time the user views the folder.
Thumbs.db files are stored in each directory that contains thumbnails on Windows systems. The file is created locally among the images, however, preventing system wide use of the data and creating additional data load on removable devices. Windows XP Media Center Edition also creates ehthumbs.db which holds previews of video files. Each thumbnail created in a directory is represented in this database file as a small JPEG file, regardless of the file's original format.
Beginning with Windows Vista, thumbnail previews are stored in a centralized location on the system. This provides the system with access to images independent of their location, and addresses issues with the locality of Thumbs.db files. The cache is stored at %userprofile%\AppData\Local\Microsoft\Windows\Explorer as a number of files with the label thumbcache_xxx.db (numbered by size); as well as an index used to find thumbnails in each sized database.
However, when browsing network shares with write permission, Windows Vista and Windows 7 store a Thumbs.db file in the remote directory instead of using the (local) central thumbnail cache. This can cause issues when deleting remote shares, as the directory will become locked for a period of time when selected as Windows Explorer automatically creates a remote Thumbs.db file.
Rebuilding the Windows 7 Thumbnail Cache
Sometimes the caches gets corrupted, and we need to rebuild them. All you have to do is open up Disk Cleanup through the start menu search box (type in "disk cleanup" to find it)
Just make sure that Thumbnails is checked, and then click OK to run through the cleaning process.