Adobe Lightroom - Corrupt Thumbnails

I just got a new Dell Optiplex 990 computer with an Intel Core i7-2600 CPU @ 3.40 GHz with 8.00 GB of RAM and 64-bit Windows 7 OS for image processing. It's fast.

I just processed 2 processed 2,297 .DNG files and exported them as Jpegs. Unfortunately, when I look at the thumbnails in Windows, this is how they look:

Click images to enlarge

I thought the files were corrupt and tried exporting them again - same result. When I opened the images the files seemed fine, but I didn't want to run the risk of corrupt thumbnails. Fortunately a post on SevenForums described the same phenomenon. Here is the solution:

Open Disk Cleanup (I just click on the Start Menu and type Disk Cleanup in the Search box).

Select the drive where you keep your thumbnails and press the OK button.

Check Thumbnails on the list of stuff to clean up (you may want to un-check all the other options) and press the OK button. This will delete all your thumbnails. When you reopen the folder your thumbnails will be fixed (they were never broken, but in the interest of speed, they were never drawn right in the first place).

"Fixed"

I hope this helps.