Way to reproduce:

• log out if you're logged in
• create a job with non-ascii characters in the name
• go to the project's page (so now you're at https://hudson/hudson/job/K%C3%B6r%C3%B6k/ for example)
• click on the login link, the link will be something like this: https://hudson/hudson/login?from=/hudson/job/K%C3%B6r%C3%B6k/ )
• log in
• and see the 404 error page from the url:
  https://hudson/hudson/job/K%F6r%F6k/