Desktop Thumbnails Images problem

I started to have this problem lately, some of my desktop image thumbnails are not showing completely ,like they are not downloaded correctly or unfinished.
It doesn't happen with all images ,but it happens pretty often.

Files affected: images - downloaded or saved on the desktop by various programs such as adobe photoshop ,photomatix HDR generated image ,mainly big image files like over 1MB.

I tried the disk cleanup thumbnail cache ,it worked recovering the unfinished thumbnails ,but it still happens again.

A restart doesn't help. And it only happens on the desktop. in folder files are fine.

Thank you.

Here's a screenshot with what's happening:

If you can still open them fine, something is corrupt in the generation process of the thumbnail images. Have you installed any codec packages on the machine?

Yes ,they open fine ,no problem.
Nope ,no codecs installed lately.

Not just lately. Have you installed any codecs on the machine at all?

Yes ,K-Lite codecs pack. But i have them installed like months ago ,and the problem appeared a few days ago...
What do you suggest?

Well, I can't say for sure, but often times such third party codec packs can corrupt the thumbnailing process. Since you've had them installed for months without a problem, it's tough to say that's your issue but it might be a good idea to completely uninstall them and rebuild the thumbnail cache again to see if the problem persists. Although the Shark007 codecs have atrocious "support", you might want to try them out instead. However, make sure you completely uninstall the k-lite codecs before doing so. Sometimes there can be issues.

Win7codecs