Starting Sept. 30, 2014, Genealogy.com will be making a big change. GenForum
message boards, Family Tree Maker homepages, and the most popular articles
will be preserved in a read-only format, while several other features will
no longer be available, including member subscriptions and the Shop.
Did the file in question actually name Elizabeth's parents, or simply provide her with the Gietsworth surname? Quick Google, FamilySearch, Rootsweb, Genealogy.com searches fail to turn up a single instance of this name, while Google suggests Tietsworth as a likely alternative (This name not only appears in each of the other genealogical databases, but would better match the traditional Dietz - perhaps the "G" was a typo?).
Regarding William's parentage, the New Jersey Germans book would appear to be in error. Hank Z. Jones recently did a book entitled More Palatine Families, and there he covered both the Kaes and Berg families, documenting their german origins. From his work, it would appear that Philip was the father of William.