=== modified file 'bin/addons/base/ir/ir_model.py'
--- bin/addons/base/ir/ir_model.py	2009-07-15 13:45:30 +0000
+++ bin/addons/base/ir/ir_model.py	2009-07-28 11:26:37 +0000
@@ -73,7 +73,7 @@
 
     def write(self, cr, user, ids, vals, context=None):
         if context:
-            del context['__last_update']
+            context.pop('__last_update', None)
         return super(ir_model,self).write(cr, user, ids, vals, context)
 
     def create(self, cr, user, vals, context=None):