Can't get redirects to work

I have custom error installed on my Drupal 6.12 site. The custom 404 page is working great, I have some PHP code in there to redirect to the correct page based on language.

I just tried to add a redirect, but it doesn't seem to be working. For example, I tried putting in;

muffin

But when I go to mysite.com/muffin it just gives me the 404 page.

Am I doing something wrong, or is there something interfering with how it works?

Thanks!