Issues in different browsers

Larry,
Sorry for the delayed response! I just ran the URL debugger on the page below:
www.flummis.net/index.php/charakter/30-a-und-b ( Debug page )

From that, it's saying there are duplicate og tags on your page.. and sure enough, there are! If you open the source HTML on your page, and search for og:, you'll see 2 separate blocks of Open Graph tags. The 2nd block is from JFBConnect. The first, I'm not sure where it's coming from. That could/likely is causing confusion to Facebook. On the page I linked to above, the first OG tags are using the following image:
www.flummis.net/images/flummi_01.jpg

Whereas JFBConnect (I think properly) is inserting the following:
www.flummis.net/images/flummis/flummis_net_00022.jpg

I don't know what the other extension is that's inserting those tags, but I'd really recommend finding it and disabling the OG features. Hopefully, that will clean you right no. As always though, if not, just let us know!

Best of luck,
Alex