Hi pen_b,
Sorry for the delay to your response.
First , since the login_chat.php returns the right value , I think the prob is not caused by the encrypted of phpbb,and then it mostly caused by the incorrect codes filled into the default.xml.If you can send us your default.xml file,we can check it further and send it back to you.
Please let us know if we can be anu further assistance.
PS: As Daniel mentioned before,to get a much quicker response , please contact us by using
support@123flashchat.com.