I'd like to add that UBB.Threads6 and UBB.Classic6 are two completely differant products which are coded in two differant coding languages (PHP vs Perl); so where a script may work for one it likely won't work for the other...
Also keep in mind that both products had differant people working on the code, and the UBB.C guru (Charles Capps) is no longer with Groupee.
The best coarse of action would be either upgrading to the latest UBB.C (which will, as allen pointed out) fix numerous security issues), or even go so far as to upgrade to the new UBB.T7.