From the Gnumeric list [1]:

The attached patch fixes the G_TYPE_ENUM/G_TYPE_FLAGS saving/restoring
to/from XML streams. Previously, the libgsf routines
glade_enum_from_string and glade_flags_from_string were unable to
determine the enum/flags type, which is required to look up strings like
"FOO_FLAGS_BAR" against the "FooFlags" type.

Not passing fundamental types to the libgsf helper in goffice didn't
have any negative consequences for me so far, and it shouldn't unless we
have non-GObject, non-flags and non-enum (i.e. weird) types that are not
fundamentals. I've added some debugging code for the purpose of
determining such issues.

[1] http://mail.gnome.org/archives/gnumeric-list/2006-November/msg00019.html