Users can't register to my board

I'm having an issue where new users can't sign up to my forum. I have been talking with the support team with phpbb about this issue. They have discovered that for some reason when you try to sign up the forum is trying to call up information from: functions_im.php. After some research it's led me back to here as the file is part of prilian. Any idea what's going on?

Here is a link to the other discussion:

http://www.phpbb.com/phpBB/viewtopic.php?p=2158488#2158488

I've no idea where the registration error (about required fields) is coming from, but the login error is discussed in this tutorial:
http://www.phpbbsmith.com/mb/about219.html