diff --git a/django/db/models/base.py b/django/db/models/base.py
index 7b299c19ac..fd29a3eaf4 100644
--- a/django/db/models/base.py
+++ b/django/db/models/base.py
@@ -10,6 +10,7 @@ from django.db.models import signals
 from django.db.models.loading import register_models
 from django.dispatch import dispatcher
 from django.core.exceptions import ObjectDoesNotExist
+from django.utils.datastructures import SortedDict
 from django.utils.functional import curry
 from django.conf import settings
 import re
@@ -220,7 +221,7 @@ class Model(object):
         assert self._get_pk_val() is not None, "%s object can't be deleted because its %s attribute is set to None." % (self._meta.object_name, self._meta.pk.attname)
 
         # Find all the objects than need to be deleted
-        seen_objs = {}
+        seen_objs = SortedDict()
         self._collect_sub_objects(seen_objs)
 
         # Actually delete the objects
diff --git a/django/db/models/query.py b/django/db/models/query.py
index a3b798debe..ae45e9580a 100644
--- a/django/db/models/query.py
+++ b/django/db/models/query.py
@@ -234,7 +234,7 @@ class QuerySet(object):
 
         # Collect all the objects to be deleted, and all the objects that are related to
         # the objects that are to be deleted
-        seen_objs = {}
+        seen_objs = SortedDict()
         for object in del_query:
             object._collect_sub_objects(seen_objs)
 
@@ -815,22 +815,11 @@ def lookup_inner(path, clause, value, opts, table, column):
 
     return tables, joins, where, params
 
-def compare_models(x, y):
-    "Comparator for Models that puts models in an order where dependencies are easily resolved."
-    for field in x._meta.fields:
-        if field.rel and not field.null and field.rel.to == y:
-            return -1
-    for field in y._meta.fields:
-        if field.rel and not field.null and field.rel.to == x:
-            return 1
-    return 0
-
 def delete_objects(seen_objs):
     "Iterate through a list of seen classes, and remove any instances that are referred to"
-    seen_classes = set(seen_objs.keys())
-    ordered_classes = list(seen_classes)
-    ordered_classes.sort(compare_models)
-
+    ordered_classes = seen_objs.keys()
+    ordered_classes.reverse()
+    
     cursor = connection.cursor()
 
     for cls in ordered_classes:
@@ -855,7 +844,7 @@ def delete_objects(seen_objs):
                     ','.join(['%s' for pk in pk_list])),
                 pk_list)
         for field in cls._meta.fields:
-            if field.rel and field.null and field.rel.to in seen_classes:
+            if field.rel and field.null and field.rel.to in seen_objs:
                 cursor.execute("UPDATE %s SET %s=NULL WHERE %s IN (%s)" % \
                     (backend.quote_name(cls._meta.db_table),
                         backend.quote_name(field.column),
@@ -877,7 +866,7 @@ def delete_objects(seen_objs):
         # NULL the primary key of the found objects, and perform post-notification.
         for pk_val, instance in seen_objs[cls]:
             for field in cls._meta.fields:
-                if field.rel and field.null and field.rel.to in seen_classes:
+                if field.rel and field.null and field.rel.to in seen_objs:
                     setattr(instance, field.attname, None)
 
             setattr(instance, cls._meta.pk.attname, None)
diff --git a/django/utils/datastructures.py b/django/utils/datastructures.py
index 4ad7bc52da..ed7a848636 100644
--- a/django/utils/datastructures.py
+++ b/django/utils/datastructures.py
@@ -60,21 +60,23 @@ class SortedDict(dict):
             yield k
 
     def items(self):
-        for k in self.keyOrder:
-            yield k, dict.__getitem__(self, k)
+        return zip(self.keyOrder, self.values())
 
     def keys(self):
-        for k in self.keyOrder:
-            yield k
+        return self.keyOrder[:]
 
     def values(self):
-        for k in self.keyOrder:
-            yield dict.__getitem__(self, k)
+        return [dict.__getitem__(self,k) for k in self.keyOrder]
 
     def update(self, dict):
         for k, v in dict.items():
             self.__setitem__(k, v)
 
+    def setdefault(self, key, default):
+        if key not in self.keyOrder:
+            self.keyOrder.append(key)
+        return dict.setdefault(self, key, default)
+
 class MultiValueDictKeyError(KeyError):
     pass