What other extensions are you using?
It sounds like you have a mix of stand alone extensions and Newer Bundled extensions (Design Extender). Make sure that you are not installing any extensions that are bundled into design Extender, refer to the following list:
-- CSS Sculptor
-- CSS Menu Writer
-- Framework Builder
-- PowerCMS Builder
-- Pro Maps for Google
-- Site Import
-- Site Sculptor
-- Social Media Toolkit
and that you don't install any of the stand alone extensions after installing Design Extender.