Hmm, ok, I just did this from the CLI and it didn't seem to throw anything up. I was initially trying to do it through my IDE (Aptana), and that was throwing up an error, saying that I needed to login to access that file.
In both occasions the files are being pulled down via SVN:Externals, as per your Wiki page.
Thanks for looking your end Sam, I guess there is an error with my software :(.
Mo