[Zope] SSL and Session Data

Is there a difference in how Zope handles session data (i.e. anything stored within the SESSION attribute of the REQUEST object) when it is running with and without SSL? For some reason, when I access Zope securely (i.e. https://...) my session data is not retained as I access different pages of my application. This does not happen when I use http://... to access Zope. I was able to determine this by using <dtml-var "REQUEST.SESSION"> in my DTML documents. Any help would be greatly appreciated. Thanks. - Asad