FYI Omegatron, if anyone else has the same problem of users who haven't activated their account logging in through the Photopost login link, I have the solution:
Copy the threads login.php and login.tmpl files to the appropriate folders in the photopost folder. Then edit login.php and change the path to main.inc.php and to the path to /ubbthreads/languages/*/login.php. Worked for me!
In my case, I had Photopost and UBB.Threads in separate folders. So I changed the path from main.inc.php to ../nameofthreadsfolder/main.inc.php. I also added ../nameofthreads before the path to the languages/login.php file.
