polymorphic join, object.destroy issue

My generic routine looks like this:

def update_linked_poly_side(base_side, ids, poly_side)
  # get back the current linked items, and the base part
  # of the polymorphic field names, like 'appllinkable'
  linked, poly_base = self.polymorphic_info base_side
  id_attr = base_side+'_id'
  linked.each do |link|
    linked_model_id = (link.send id_attr).to_s
    link.destroy unless ids.include(linked_model_id)
  ids.each do |id|
    linked.create(blah blah blah - create works fine)

The link.destroy works fine for the first link that is currently
linked but isn't in the ids list, but it doesn't work for any
subsequent links that should also be destroyed.

Runtime logging (not in the code above for clarity) reports:
at entry,
  3 appllink objects, ids ["3", "1", "2"] in linked (correct)
  poly_base = 'applinkable' (correct)
  ids = ["", "2"]
  in the linked.each do |link| loop
  it looks for "3" in ids, doesn't find it and logs:
    SQL (0.000694) BEGIN
    Appllink Destroy (0.000345) DELETE FROM 'appllinks'
      WHERE 'id' = 9
    SQL (0.001159) COMMIT

  then it looks for "1" in ids, doesn't find it and logs:
    SQL (0.000138) BEGIN
    SQL (0.000137) COMMIT

There isn't an issue with the first linked item that is to be deleted,
but there isn't a SQL statement generated for any subsequent items that
should be removed... adding new linked items works just fine (that's in
the ids.each do |id| loop).

Any ideas? Anyone? Oh, and Rails 2.1.0, Ubuntu 8.04, Ruby 1.8.6