IE Doubling Margin Width

Take a look at this page in Firefox and IE:
http://www.solardreamstudios.com/

You'll notice that the thumbnail image in the news post has a larger margin spacing in IE but not in Firefox or Opera or Safari. I can not for the life of me figure out what is causing this.

I want it to look like the Firefox version.

I can apply a hack so that IE renders it correctly but I still don't understand why IE takes a margin: 10px and renders it exactly 20px. This only happens in this certain instance. IE renders all of my other Margins with floats perfectly fine.

Does anyone know why this is happening?

Thanks.