Even with $auth_time set to insanely high values (say, 86400), logins expire
immediately. Within seconds - actually, the very next time db.cgi is called - logins expire, returning the `invalid/expired user session' page.
I've been seriously hacking on html.pl, but I can't imagine offhand how changes there could affect auth.pl.

The only significant change (Perl-wise) I've made to html.pl is adding a few calls to stat() and `use File::stat' for them. I'm kinda out of ideas at the moment...