The issue as lat9 is trying to lead you to is now identified not to be a file issue, but now is a database issue. In your old store, even though you may not have had phpBB installed, it was activated before upgrading the database... Now in zC 1.5.4 the software goes out and tries to do something based on that setting and stops working...
Now you need to change the setting in the database so that it doesn't go out and do that... Not at a computer to specifically identify the sql that will specifically solve the problem.




