Fatal Error at registration ??

[PinkDaisy]

Fatal error: Existing data passed is not an array
Called set_existing in /home/belliesb/public_html/forums/includes/functions_databuild.php on line 164
Called build_forum_counters in /home/belliesb/public_html/forums/register.php(507) : eval()'d code on line 162
Called eval in /home/belliesb/public_html/forums/register.php on line 507
in /includes/class_dm.php on line 235

The above is the error I get when I was testing registrations. It seems the registtration actually goes through for the user, but after they hit the register button and fill in their info, this is what is shown. Any ideas on what this could be??

Thanks for any help and tips!