http://forums.kc-mm.com/index.php?topic=9248.0this should help.
but there's 2 ways to fix this, but since you're doing a one slot swap, do this. rename Ness's third bone (bone index 2) to TransN, and rename his current TransN to something else, then it will work. what you should do is rename the index 2 bone to TransN, index 3 bone to XRotN, index 4 bone to YRotN (the current TransN), and index 5 bone to HipN (the current XRotN), and the index 6 and 7 bones to something else (doesn't matter what they're named, but there the current YRotN and HipN bones). that way, it will also correct a few other glitches you probably haven't found yet, mainly the grabbing and being grabbed glitch.
if you have other questions, just ask. my guide should also help if you have other issues that come up.