You didn't just copy the link location, which should be something like:
http://content.screencast.com/users/jpartner/folders/5-20-2013/media/4a40b321-22f6-4099-bb50-becac66a587f/SLIDE%201.png
Your link had a bunch of HTML code in it. Maybe screencast.com makes it difficult to copy links to protect their content? Trying the same with the HTML editor and the "Insert/edit image" icon: 
Trying the same with copy and pasting directly from MS Paint to NAT: 
Edited by Chimel 5/27/2013 02:40
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html picture issues
