While I'm coding in various buffers, sometimes semantic/cedet wants to delete some buffer(s) I'm not immediately using.  The clue:  A pop-up window saying words to the effect of 
   "foo.cpp has been modified.  Do you really want to kill it"

This would appear to correlate with this entry in *Messages*:
   Updating buffer list...done

I think its frequency depends on how many files I'm working on at the same time, but I have not figured out how to readily reproduce it.

I would think semantic would only delete buffers that:
1) it -- not the user -- has opened, and
2) are not modified.

Is this the case?  If not, should it be?

If there's some configuration associated with this behavior, please advise.