"create issue" link broken from a custom domain.

Adding new issues from the custom domain interface does not work, since the initial username part of the URL is omitted for all links, but the "create issue" button still submits to a URL with the initial user name.

For example, I'm trying to submit a new issue by filing out the form at http://hg.pynac.org/pynac/issues/new. After hitting the "create issue" button, I get a 404 error from http://hg.pynac.org/pynac/pynac/issues/new.