diff --git a/django/contrib/contenttypes/generic.py b/django/contrib/contenttypes/generic.py
index b738a269ec..63c44ab285 100644
--- a/django/contrib/contenttypes/generic.py
+++ b/django/contrib/contenttypes/generic.py
@@ -137,6 +137,11 @@ class GenericRelation(RelatedField, Field):
 
     def get_internal_type(self):
         return "ManyToManyField"
+
+    def db_type(self):
+        # Since we're simulating a ManyToManyField, in effect, best return the
+        # same db_type as well.
+        return None
         
 class ReverseGenericRelatedObjectsDescriptor(object):
     """
diff --git a/django/db/models/sql/query.py b/django/db/models/sql/query.py
index 97b4ee1a47..6302416b41 100644
--- a/django/db/models/sql/query.py
+++ b/django/db/models/sql/query.py
@@ -528,7 +528,8 @@ class Query(object):
         self.where.add([alias, col, orig_field, lookup_type, value],
                 connection)
         if negate:
-            self.alias_map[last[0]][ALIAS_JOIN][JOIN_TYPE] = self.LOUTER
+            if last:
+                self.alias_map[last[0]][ALIAS_JOIN][JOIN_TYPE] = self.LOUTER
             self.where.negate()
 
     def add_q(self, q_object):
@@ -770,7 +771,7 @@ class DeleteQuery(Query):
                         ContentType.objects.get_for_model(cls).id), AND)
             for offset in range(0, len(pk_list), GET_ITERATOR_CHUNK_SIZE):
                 where = WhereNode(self)
-                where.add((None, f.m2m_column_name(), None, 'in',
+                where.add((None, f.m2m_column_name(), f, 'in',
                         pk_list[offset : offset + GET_ITERATOR_CHUNK_SIZE]),
                         AND)
                 if w1:
diff --git a/django/db/models/sql/where.py b/django/db/models/sql/where.py
index 7c27fc92b3..5995f83486 100644
--- a/django/db/models/sql/where.py
+++ b/django/db/models/sql/where.py
@@ -87,7 +87,8 @@ class WhereNode(tree.Node):
             lhs = '%s.%s' % (table_alias, conn.ops.quote_name(name))
         else:
             lhs = conn.ops.quote_name(name)
-        field_sql = conn.ops.field_cast_sql(field.db_type()) % lhs
+        db_type = field and field.db_type() or None
+        field_sql = conn.ops.field_cast_sql(db_type) % lhs
 
         if isinstance(value, datetime.datetime):
             # FIXME datetime_cast_sql() should return '%s' by default.