Index: django/db/models/options.py
===================================================================
--- django/db/models/options.py	(revision 6440)
+++ django/db/models/options.py	(working copy)
@@ -152,7 +152,7 @@
             rel_objs = []
             for klass in get_models():
                 for f in klass._meta.fields:
-                    if f.rel and self == f.rel.to._meta:
+                    if f.rel and not isinstance(f.rel.to, str) and self == f.rel.to._meta:
                         rel_objs.append(RelatedObject(f.rel.to, klass, f))
             self._all_related_objects = rel_objs
             return rel_objs
@@ -186,7 +186,7 @@
             rel_objs = []
             for klass in get_models():
                 for f in klass._meta.many_to_many:
-                    if f.rel and self == f.rel.to._meta:
+                    if f.rel and not isinstance(f.rel.to, str) and self == f.rel.to._meta:
                         rel_objs.append(RelatedObject(f.rel.to, klass, f))
             if app_cache_ready():
                 self._all_related_many_to_many_objects = rel_objs
Index: django/core/management/validation.py
===================================================================
--- django/core/management/validation.py	(revision 6440)
+++ django/core/management/validation.py	(working copy)
@@ -70,10 +70,11 @@
             # Check to see if the related field will clash with any
             # existing fields, m2m fields, m2m related objects or related objects
             if f.rel:
-                rel_opts = f.rel.to._meta
                 if f.rel.to not in models.get_models():
-                    e.add(opts, "'%s' has relation with model %s, which has not been installed" % (f.name, rel_opts.object_name))
+                    e.add(opts, "'%s' has relation with model %s, which has not been installed" % (f.name, f.rel.to))
+                    continue
 
+                rel_opts = f.rel.to._meta
                 rel_name = RelatedObject(f.rel.to, cls, f).get_accessor_name()
                 rel_query_name = f.related_query_name()
                 for r in rel_opts.fields:
@@ -101,10 +102,11 @@
         for i, f in enumerate(opts.many_to_many):
             # Check to see if the related m2m field will clash with any
             # existing fields, m2m fields, m2m related objects or related objects
-            rel_opts = f.rel.to._meta
             if f.rel.to not in models.get_models():
-                e.add(opts, "'%s' has m2m relation with model %s, which has not been installed" % (f.name, rel_opts.object_name))
+                e.add(opts, "'%s' has m2m relation with model %s, which has not been installed" % (f.name, f.rel.to))
+                continue
 
+            rel_opts = f.rel.to._meta
             rel_name = RelatedObject(f.rel.to, cls, f).get_accessor_name()
             rel_query_name = f.related_query_name()
             # If rel_name is none, there is no reverse accessor.