i'm working on a similar project, and on the server i'm working with, it requires some headers to be set. (request.setHeader("Referer", "chrome://myscript") in my case) so check to see if that's the case with the server your working with. if you don't have direct access to the server, the FireFox extension "Live HTTP headers" is a godsend. i'll see if i can find the address to the extention in a min, but its on the official extention site. hope this helps!
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