Unable to import png files: more information

Hello, I got the latest version of Synfig on Windows 7, no installation problem.

wen I try to import png, I can do it for a few images and it’s all ok, but at 9°, 11à, 12° or 13° imnage I try to import it tells me: “Unable to import png”. After that, it cannot import no longer any png.

My images are not heavy, less than 1 Mb, th ewhole image is about 10 Mb.

Images are made in GIMP, in RGB mode.

Why?

How can I solve my problem?

Please share one of the problematics png images to test it out in other system.
-G