If this is occuring from first loading and its at a zero pose and IK's off then its not jointing that is causing it. Even if the joints are incorrect, at zero it would hold together...... OK we now get into the land of Ig ... (Intelligent guess work :) Try another PHI with no curves. I'm looking at the way you have sectioned the neck. Each group has very little for the curve parameter to work on. I think I would have been tempted to group in rings of 3 sections rather than singles. And thanks for the thanks its appreciated :)