…I’m not the guy who originally wrote this article, but I’ll do what I can! ;-)
The complaint that the “request for <http://…valid url> failed” seems to indicate a url-resolution problem, but it’s hard to tell because the error message doesn’t specify the exact problem.
…as the guy who had written it: The URI printed out by line 112 (Fetching/processing…) is the URI that actually will be fetched.
Some additional things that could go wrong: