Well I can't really say anything without actually seeing your data but as I said switching integrations is something we really do not support overall since it relies heavily on forum import scripts and how they import data for us to match users.
Switching from phpbb to vbulletin
That is a step by step tutorial.
You really want to start with a database backup of your photopost tables before you switched to xenforo and do the steps meantioned.
You will know if your correctly integrated and running right with xenforo when your done. Once your sure of that you can try running userfix but not before making sure you have installed correctly to integrate with xenforo.
If you ran userfix when your integration was not 100% into the new forum you could essentially mess up ownership of photos comments and albums.