Twenty Eleven – Gallery Post: Thumbnail not shown

Hi,

Twenty Eleven is a great theme, it supports all what I need for my site. But, I found a problem in the IE8:

When you visit https://event.sandrophoto.ch/, you see one thumbnail at the “Gallery”-Posts with all browsers, but the big exception is one more time the IE. But the funny thing is, that the thumbnail is shown, when you’re in the compatibility mode.

I don’t know, where the problem could be…

Do you know this problem or do have any idea to come closer to a solution?

Thanks!