If you are getting a demo-only message appear after you have edited text and when you try and save your changes, please try the following:
Tools menu > Internet Options > Security Tab, then click [Default]
Tools menu > Internet Options > Privacy Tab, then click [Default]
Tools menu > Browsing History > Delete, then click [Delete temporary internet files] and [Delete cookies]
Then click [OK]
Please also try closing all your browser windows and starting a completely new session.
Further related help is found here