[Zope] CMF import issue

Hi I imported a CMF site into my zope installation from another zope installation. I have the 2.6 version while this site was installed on 2.5.1 version. Plone extensions are used in the site as well. Although my import was successfull I could not import a lof of objects including ones under portal_skins/Images and many others. Also the site does not seem to function on my installation. Is there something I should know of here? Appreciate your reply