Description:
------------
So far as I can tell this problem is trigged by the serialisation/deserialisation 
going on in the inheritance hierarchy (ParentA and ParentB) in combination with 
the re-use (triggering obj references in the serialisation) of ParentB's children 
in Wrapper.

At a guess this is a difference in the table construction between serialize and 
unserialize (thus ending up referencing the incorrect thing), but I haven't yet 
taken a look at their implementation so that's a total stab in the dark.

Test script:
---------------
http://pastie.org/private/vbjpi8ytmqqxi2pkiizatw

Expected result:
----------------
object(Wrapper)#6 (2) {
  ["parent"]=>
  object(ParentB)#7 (2) {
    ["collection"]=>
    array(3) {
      [0]=>
      object(Child)#8 (1) {
        ["property"]=>
        string(3) "foo"
      }
      [1]=>
      object(Child)#9 (1) {
        ["property"]=>
        string(3) "foo"
      }
      [2]=>
      object(Child)#10 (1) {
        ["property"]=>
        string(3) "foo"
      }
    }
    ["rofl"]=>
    string(3) "foo"
  }
  ["children"]=>
  array(3) {
    [0]=>
    object(Child)#8 (1) {
      ["property"]=>
      string(3) "foo"
    }
    [1]=>
    object(Child)#9 (1) {
      ["property"]=>
      string(3) "foo"
    }
    [2]=>
    object(Child)#10 (1) {
      ["property"]=>
      string(3) "foo"
    }
  }
}

Actual result:
--------------
object(Wrapper)#6 (2) {
  ["parent"]=>
  object(ParentB)#7 (2) {
    ["collection"]=>
    array(3) {
      [0]=>
      object(Child)#8 (1) {
        ["property"]=>
        string(3) "foo"
      }
      [1]=>
      object(Child)#9 (1) {
        ["property"]=>
        string(3) "foo"
      }
      [2]=>
      object(Child)#10 (1) {
        ["property"]=>
        string(3) "foo"
      }
    }
    ["rofl"]=>
    string(3) "foo"
  }
  ["children"]=>
  array(3) {
    [0]=>
    object(Child)#9 (1) { <-- Where'd #8 go?
      ["property"]=>
      string(3) "foo"
    }
    [1]=>
    object(Child)#10 (1) {
      ["property"]=>
      string(3) "foo"
    }
    [2]=>
    string(20) "1Y"  <-- Unexpected
  }
}