What usually causes this problem is the ServicePointManager throttling concurrent requests to the same URI which leads to response time-out issues. I find it hard to fathom how such would be possible in this instance. So without more information, like the http response code, I've reached to end of my expertise.
One thing you might try is opening "http://content.turbine.com/sites/clientsts/ddo/en/ddo_generic_teleport_screen_2.jpg" in your browser repeatedly. Using IE (best way I'm afraid), navigate to the URL and then hit Ctrl-F5 to refresh it as quickly as possible. If at any time you get an http exception, make note of it and let us know what it is.
Best of luck!