Hmmm... I have a similar problem.
Basically for each new subsite I make, it becomes a part of subsite1 (the first client). I never bothered correcting, its in heavy production state. So I just remove the Composition after each new client subsite.
Could it be related to the bug that I found regarding the group of a site is not created until you visit the group page? Weird. Although in your case I think its more of a context_id problem.
Maybe an ubber hacker can track this down... ever heard about Don Wickstrom?
