Authenticating against dev.rubyonrails.com?

When trying to execute the command ‘svn checkout
http://typosphere.org/typo/trunk typo’ it starts to pull the down the
files
as normal, but eventually says it’s fetching an external item into
typo/vendor/rails and it prompts me for a password for
dev.rubyonrails.com.

Has anybody encountered this? It would seem like a pretty common problem
since it’s preventing me from even pulling the source down.

Thanks!