black thumbnails in vista mce help

[kittysacattack]

I used to have images for all my dvds in vista mce, but for some most of the squares are black now. If anyone knows about this, you help would be greatly appreciated. Thanks.

 

[kittysacattack]

I noticed the disc cleanup tool reomoves thumbnails. Could this be the cause, and if so, how could i restore them?

 

[alexyu]

restore a system restore point created before icons became black