By login loop do you mean it logs you in but as soon as you click a link it logs you out?
Yes, this is exactly what the problem is.
The admin loop happens when you upgrade your files from Advanced Guestbook 2.2 to 2.3.1.
To my knowledge, I never upgraded. Only after the hack did I notice this problem. I guess that means he brought this on?
The alternative is to either apply the patch yourself or goto www.carbonize.co.uk/AG and download the pre patched file.
I am assuming that using this alternative (2.2 to 2.3.1 Database Upgrade Script) will also not bring the pictures in?
I think Carbonize has recommended that you use his password reset script to help resolve this problem.
I am also assuming this is incorrect.
BTW the site you mention had three hacked entries one of which took you to a fake Yahoo login screen which i have now reported.
Very cool, thanks for reporting! He goes by (and apparently answers to) the email net_devil@hackermail.com. All of his hacks are somehow updated daily on the list on this website: http://www.zone-h.org/en/defacements/filter/filter_defacer=nEt%5EDeViL/page=2/.
Thanks again for the help!