JC posted a link to a post about 6.5 <img src="https://www.ubbcentral.com/boards/images/graemlins/tongue.gif" alt="" /> - but it doesn't really relate as your question was about 6.4.2. Thats a bug - the jumper is broken in 6.4.2 (as you'll see even here at this board). I posted this fix in this thread:
https://www.ubbcentral.com/boards/showflat.php?Number=36567
