[Plugin: NextGEN-ImageFlow] Only empty square thumbs

I’m going to become mad.
Searching all around the web, I didn’t find nothing to solve this problems.
Instead of the thumbs, i only have a square image, empty, that respects the ratio of the original image, but isn’t displayed. If I click on it, I have the full image on the browser, no effects.
It looks like it isn’t able to generate thumbnails.
The files (reflect2 and 3 ) are properly allocated in the root of Wp.
Any help is highly appreciated.