Moved from the Creative Cloud to the InDesign forum. They will be able to help you here.
Are you certain both computers have CC 9.1 on them? The error sounds like what you would get opening a CC file in CS6. I haven't heard that 9.0 cannot open 9.1 files, but I suppose that's also a possibility.
Are you using a Wacom tablet? There are som known issues withthe Wacom drivers and saving in CC.
Are you sure about that? Under the InDesign menu on both machines cmd+click About InDesign.
You'll get full build and version number information that way.
I am having a similar issue. Allthough everything works fine on my MacBook I can't save certain files and the undo does not work on my iMac. I am using CC 9.1 on both machines.