I had similar issues with Trac, and contacted support. Their reply was:
[font=Courier]Thanks for contacting us on this! I am happy to explain! Our Trac
install does not actually support the normal users and logins. The only
logins that work for our install are those tied to the Trac through SVN
and then only for accessing the site, not for logging in to the
I couldn't work out what to do from this and uninstalled. Maybe it'll be more use to you.