[heis]

I'm new to using master document/ sub documents function in MS word.
I have a question regarding that. I've created a master document with
several subdocuments. Several times, when I open the master doc, some of the
subdocuments are not there. Yes, I think I've made some changes to those sub
documents but never changed either the names nor the locations of those
subdocuments. It feels like I'm using a feature that is not stable enough
which makes me quite nervous about using this. Does any of you know what's
going on or any suggestion regarding how to use this feature more
effectively? Any known bugs or etc.? Thanks a lot!