Some thumbnails doesn't work (and it's not the 3MB limit)

Sorry for my English, it’s not my native language.
So people, I’m using openSUSE 12.1, KDE 4.8.1 “release 483” and Dolphin 2.0. Some thumbnails doesn’t load properly and it isn’t because the Dolphin restriction about the file sizes. In Dolphin preferences, where it says “Show previews for” only “Images (GIF, PNG, BMP…)” and “JPEG Images” are selected. Where it says “Do no create previews for local files above:”, I set it to 15 MB (I download very large pictures).
In fact, many of the pictures of which Dolphin doesn’t show thumbnails are 1MB or less. Filenames are short too and file extension is .jpg
When I open the pictures with Gwenview, I can see the pictures without any problem.

At first I thought it was something about “Interlace Mode”. Almost all the pictures which doesn’t load says “Interlace Mode: false” in the information tooltip. But there are pictures which says that and Dolphin shows the thumbnail anyways. Some pictures doesn’t have that interlace thing, and Dolphin still doesn’t show a proper thumbnail. I’ve looked everywhere, but I haven’t found anything, so please help me. I don’t have the slightest idea about this.
Thanks in advance.

I see this with one or two images
But they are not images of mine (that is produced by me in any way). I suspect they are created in some way and on some other system that makes them this way.

If I open one of such in Gimp
It asks me to manage the transparency, so I choose ‘Export’
And save it at 100%
Now the file thumb works