that is correct, that feature belongs under Chatters limit "plan" and that is why it costs $0.00 (it is included if you select any Chatters limit)
Basic chat is free, but all of your members are treated as guests = database integration is not free, it is a subscription based feature now.
Change from totally free all features included chat into new subscription based features system has been done at 9th July 2008 at 00:00 GMT (that is why it worked "fine" yesterday and today you think there are some problems.
In other words, username integration is not free anymore.
You can explore our subscription plans and feature options in admin backend under menu Components - BlastChat client - Configuration - Server side Configuration (if you do not have this menu you are using old BlastChat version), or at
www.blastchat.com "Your registration" menu link.
Our introductory pricing is very low and the very cheapest plan which enables discussed usernames integration costs "Less then a $1/month".