[Plugin: Grou Random Image Widget] Displaying some images adding ._ in front of others

I installed the plugin and got it working for the most part. Every few pages loaded the plugin places a “._” in front of the images url and shows a broken image link. For example: region.jpg turns into ._region.jpg and shows a broken image link. Any idea what’s going on?

http://wordpress.org/extend/plugins/grou-random-image-widget/