[Zope] Frequent Zope Restarts and GUF authentication

I have a server that is being run in production mode without the -D flag. The server processes die after about two hours. I haven't seen the actual crash yet nor have any users complained about error messages. I know the server is restarting because the Control_Panel tells me so. Well, the real problem here is that since my site is protected with GenericUserFolder in cookie mode, GUF's cache gets wiped when the server bounces. This forces my users to log in again. Two questions, Any guesses as to what's causing the mysterious restarts? Any idea on how to resolve the GUF problem? -Jon