You could try unzipping the capx by renaming it to boatymcboatface.zip. Then open the New project.caproj into your xml editor.
Replace <saved-with-version>24100</saved-with-version>
With <saved-with-version>23300</saved-with-version>
Save it, and you should be able to double click the caproj for editing.
I don't think there were any changes to those objects between the updates.