Right, looking at that you should have no problems hosting JJ2 games as long as you allow them through your firewall (and if you don't have a firewall, then get one *now* - ZoneAlarm is a good free one).

You say you can host games fine with 1.23 and TSF, but not 1.25? In that case, you'll have to poke unknownfile to find out what he changed.