Probably not the source of your headaches, but you probably want lastUpdate to be "auto_now=True":
lastUpdate=db.DateTimeProperty(auto_now_add=True) -- You received this message because you are subscribed to the Google Groups "Google App Engine" group. To post to this group, send email to google-appengine@googlegroups.com. To unsubscribe from this group, send email to google-appengine+unsubscr...@googlegroups.com. For more options, visit this group at http://groups.google.com/group/google-appengine?hl=en.
