Instructional Design Storyboards

I am trying to find a tool for writing elearning storyboards that can provide the flexibility of Word (at least with tables and rough image manipulation and floating objects)and/or Powerpoint but with a foolproof colaborative edit and review functionality (anything better than Word's Track Changes). Show seems to be the go but it feels a little quirky and unstable and the use of tables in Show is very clunky - have to copy from Write.
Any ideas or help in creating complex tables and floating text boxes and images in one app?
jim.marjoram