Weird box showing up in posts

I am having the exact same problem. For me it has something to do with having the Recent Posts widget in my sidebar. If I take it away, the box goes away. If I put it back it comes back. It only does this in my sidebar. If I move it to my footer then I don’t get a box. There was a previous message about this and someone said it was due to the Simple Sharing plugin which I don’t have installed on my blog. Not sure what the problem is though but I would like to figure it out because I had having my recent posts listed at the bottom of my blog.

Does anyone have any other ideas what it could be? I would be grateful.