Boh sets of docs: Just to follow up on this: last month I got the same error as Ralf, but I ignored it and continued, and the page did not create. But I have waited acouple of week and now I still get the error, but the page seems to create perfectly.
ie Trying to create User:name/pagename has a false error message on the way as picture in Ralfs post.
I can guess at the problem. User pages in wikipedia are based on USERNAME. Pages here are more civilised and based on NAME. Maybe a small setting out of wack.