Strange Problem with latestnews+ - Thumbs not showing

I´m currently upgrading an J1.5 website to J2.5 and are experiencing a strange problem. On the main page the thumbnails in latestnews+ are shown correct - if I choose e.g. "bildergalerie" (i.e. JoomGallery) only the placeholder is shown.
Does anyone have an idea what could be the problem?
TIA

I've visited on both main page and Bilder Galerie page and latestnews looks fine on both....