CDN Images don't Load (OpenGraph)

I setup in my wordpress blog OpenGraph. For image I insert this code (wordpress): http://dl.dropbox.com/u/21385868/codeog.jpg

the result in site page (html is): http://dl.dropbox.com/u/213开发者_如何学运维85868/resog.jpg

if I share article on the facebook, image don't appear. But, if I disable my cdn, image appear on the facebook.

What is the problem?

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In Advanced CDN settings add to Rejected User Agents

    FacebookExternalHit/1.1
    FacebookExternalHit/1.0

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Facebook blocks images that are hosted on CDNs.