Hello,
Yes it's a nice way to how explain how to

, it was done with build demo.
Maybe Photopost should do a serie for their soft... for V5.0 for example.
Anyway, so your problem, can you check as well in phpmyadmin if your usergroup table (photopost one) is empty or not ?
If it's empty, execute the mysql command:
INSERT INTO `pp_usergroups` VALUES (6, 'Administrators', 1, 1, 1, 0, 0, 1, 1, 0, 0, 0, 0);
Then try to log in again, if it's successful, go to your pp admin area and refresh the usergroups, then you are done.
Later,
Interdit