Well, I finally ran out of excuses to keep putting it off. So I've created a page on meta ( http://meta.wikimedia.org/wiki/Multilingual_error_messages ) to start off the process of redesigning the Wikimedia server error messages. I find it unacceptable that all wikis - regardless of their setup language - receive the same English language message. We also need to do things like remove the link to OpenFacts, because that site gets overloaded within a few seconds of any Wikipedia downtime.
I welcome any comments whatsoever on this project.
~Mark Ryan