I get the same issue.

<form method="POST" action="default.asp">

You'd put a user/passcode to get the the site via form.
Is there a program that allows that?
The .htaccess (login/pw) right up front, HTTrack can handle
that.

WHAT ABOUT using the SAVED COOKIE from the site when logged
in via IE or Mozzila, than PLACE THAT cookie in the HTTrack's
directory than everything would be fine because once logged in
the cookie is saved...