UBB.threads PHP Forum Software Community Forums UBB.threads Version 7/8 Support Help - Fatal error: Call to a member function error() on a non-object mysql.inc.php on line 77

Well then you are back to discovery mode.

If you can't figure it out there are resources to explore.
Open a support ticket.
Hire somebody to look into it.

But the bottom line is everyone is going to suggest as a bare minimum is to upgrade.