Are the login issues on the front-end or back-end? If you set your site to offline then it should not allow you to get in the front-end... and you would need to login in the back-end and set it to online again...
It is very difficult to debug if you don't tell me what you did... I don't see much in the phpBB connector code that could cause what you are describing but here is how you can modify the databases to get back to what you had...
(assumes you have jos_ prefix set for Joomla tables... their default)
go into jos_comprofiler_plugin table
Browse through the data... go to the "phpBB Connector" row (should be in name) select that row for editing... now changed published from 1 to 0... This will unpublish the connector so that it does not run anymore.
Then go into jos_users table...
browse through the data...
select the admin user you are having trouble with...
change the user_password to:
098f6bcd4621d373cade4e832627b4f6
this should make your password "test" (without the quotes)
Then log into the backend with your recently changed username and password.
I followed all the instructions..But it still wont let me log in..
I basically followed the connector instruction..imported all users..Everything was working 100%..then i logged out..Now i cannot get backinto my admin..No matter what i try do..
I can give you FTP access if you want..But i really need drastic help..i was ready to go live until this happened...