I have the same type of error. You found the cause of this error? If so, can it be publicly exposed? Thanks!
wignut, had a problems with additional bridge he was using integration mod between Joomla and phpBB. If you refer to the first post you will see the update in it about this issue.
1. does it work with 1.7.6 ?
It should work, however I recommend you update to 1.7.7 as it includes some important fixes and updates.
2. you say it does login from the phpbb database... how does it works ? if user is connected to the gallery page and he tries to login, hitting login button will call a file from the phpscript? or he has to first access the forum sistem and them do login ?
After user click on the button 'Login' he will be forwarded to the phpBB login page and will be logged in by phpBB application using data user inputed into the form on the gallery page.
3. is it possible to use 4images DB for login? after logout to be redirected to gallery page?
4images will use it's own database and tables for everything it was using it before.
4. what about existing users ? are they lost ?
No they will not in both applications. Existing users into phpBB application will be able to login to both application after mod installation. 4images will not be able to login into any of applications. I have in my task list create a user export from 4images to phpBB, but can't give you any estimate at the moment. And of course do backups before playing with not only this one mod but any modifications you do with any application.
5. both sistems share the same session ?
Yes.
6. what about for registration ? calling the registration form from gallery or forum is the same ?
Registration link from 4images leads to the phpBB registration page.