This is a long shot, but here goes:
I'm an ex-Animation Master user. In this program just like in XSI, there is the ability to apply an 'Orientation' constraint to a bone. However, in addition there is an option called 'Apply before action' which basically means you could continue to freely rotate this bone even though it's initial orientation would follow whatever it was constrained to.
A good use for this would be to keep a character's head level while say it's torso rotated. I know I can create a similar effect by having a parent and child bone, constraining only the parent bone which would allow me to rotate the child bone independently. Unfortunately, I overlooked this option and have already enveloped my rig.
Is there an equivalent 'Apply before action' option in XSI?