I've been a happy user of photopost for a number of years. The database problems I had meant that I was forced to redo everything and start afresh.
I used the latest copy of photopost, 5.13 I think, and a 7.6 php-nuke.
All I can say is that the install script doesn't take the domain correctly into the database. Under pp_settings (I think) there are a number of references to www.domain.com
whether you input the correct domain or not. There are also a number of paths that are screwed up - forward slash missing from places.
The biggest problem when trying to incorporate the php-bb/php-nuke user database was, for me, the lack of any data under the usergroups entry. I had to manually input three groups and give them all admincp access to get into the system. Then I could import the usergroups from the integration link. I still had to then change the admin-cp access on my account after I had done this.
All in all, I am not 100% happy with the amount of fiddling I've had to do, but upgrades through the last 2 years have worked seamlessly. I suggest that someone at Photopost should take a vanilla version of a php-nuke setup and try to install onto that. I reckon that there are issues with the install script.