diff -r 3f91fa6ba472 db/models/fields/__init__.py
--- a/db/models/fields/__init__.py	Wed Jul 07 17:22:15 2010 -0400
+++ b/db/models/fields/__init__.py	Wed Oct 06 12:41:37 2010 -0400
@@ -168,15 +168,25 @@
             # Skip validation for non-editable fields.
             return
         if self._choices and value:
+            choices_dict = dict()
             for option_key, option_value in self.choices:
                 if isinstance(option_value, (list, tuple)):
                     # This is an optgroup, so look inside the group for options.
                     for optgroup_key, optgroup_value in option_value:
-                        if value == optgroup_key:
-                            return
-                elif value == option_key:
-                    return
-            raise exceptions.ValidationError(self.error_messages['invalid_choice'] % value)
+                        choices_dict.update({optgroup_key : optgroup_value})
+                else:
+                    choices_dict.update({option_key : option_value})
+            _value = value
+            if not isinstance(value, (list, tuple)):
+                _value = [value]
+            invalid_v = []
+            for v in _value:
+                if not choices_dict.has_key(v):
+                    invalid_v.append(v)
+            if invalid_v.__len__() > 0:
+                raise exceptions.ValidationError(self.error_messages['invalid_choice'] % invalid_v)
+            else:
+                return
 
         if value is None and not self.null:
             raise exceptions.ValidationError(self.error_messages['null'])