FLAgallery – Cannot Edit thumbnails

I cannot edit my thumbnails in FLAgallery. I go to my gallery, click the “Edit Thumb” link and a little window comes up with my image, but cross-hairs do not appear over the image (as shown in tutorial). When I click and drag on the image, all that happens is that the image drags along too…

I use Mac. It doesn’t work on Safari or Chrome.