XSI 5 : weird hand spinning when splining

okay, another weird splinning question. when i spline my hand bone (or go to linear), sometimes it twists like crazy on the interpolation. i've seen this in pretty much every program ive used, but i have no idea what causes it or how to prevent it. my hand bone (or rather it's root) is postion constrained to the ik effector of the arm, if that might be causeing it. techincally the animation editor is doing its job (its certainly my fault), all the key frames are connected with linear curves, but hand will usually rotate all the way around to get to the next key frame, for example.