I don't know if you have figured this out or not. I spent several hours
investigating this issue today and I was finally able to download my phpBB
site login as the administrator. Here is what I did:

1. Using capture URL and filled in user name and password.
2. Login to the phpBB site and use "Export Cookies" extension in Firefox to
export the cookies
3. Copy cookies.txt to the root directory
4. Copy and paste Browser ID from the "hts-post0" file in the root directory
to the Set Options-->Browser ID
5. Exclude log out address in the Set Options. If you are using phpBB, the
rule should look like this
-http://foobar.com/forum/ucp.php?mode=logout*
6. Because I don't intend to download the control panel, I also exclude the
link to the control panel.
7. Finally, keep your Firefox open to the site you want to download

That's it. Good luck to you!