This will probably only add to the confusion, but I've found it very
useful in dealing with punctuating the "because" clauses.  If the
"because" clause gives a REASON, no comma is needed.  If the "because"
clause gives evidence (not reason), use a comma.

      Mrs. VG has gone home because she became ill.

      Mrs. VG has gone home, because her car is not in the parking lot.

In the "evidence" sentence, one can mentally insert "I know that" between
"home" and "because."  The comma takes the place of the "I know that."

I've never seen it in a text (except my own!)--but it works!