Index: CHANGES.txt
===================================================================
--- CHANGES.txt	(revision 128543)
+++ CHANGES.txt	(working copy)
@@ -5,9 +5,8 @@
 3.6.4 (unreleased)
 ------------------
 
-- Nothing changed yet.
+- Fix translate() when used with ZODB 4.
 
-
 3.6.3 (2010-09-01)
 ------------------
 
Index: src/zope/app/i18n/translationdomain.py
===================================================================
--- src/zope/app/i18n/translationdomain.py	(revision 128543)
+++ src/zope/app/i18n/translationdomain.py	(working copy)
@@ -23,7 +23,6 @@
 import zope.component
 from zope.interface import implements
 from zope.i18n import interpolate
-from zope.i18n.negotiator import negotiator
 from zope.i18n.interfaces import INegotiator, ITranslationDomain
 from zope.i18n.simpletranslationdomain import SimpleTranslationDomain
 
@@ -71,7 +70,10 @@
             target_language = negotiator.getLanguage(avail_langs, context)
 
         # Get the translation. Default is the source text itself.
-        catalog_names = self._catalogs.get(target_language, [])
+        if target_language is not None:
+            catalog_names = self._catalogs.get(target_language, [])
+        else:
+            catalog_names = []
 
         for name in catalog_names:
             catalog = super(TranslationDomain, self).__getitem__(name)