Richard, are you opening the working version of the Master project (the default open)? If you are, try opening the published version. Access the project open dialog box and select open from the Published store. That will automatically open the project read only. To the best of my knowledge, opening the working version will automatically update to the working versions of the sub-project. Another try is to open up the master project read only. I’m not sure that will work and I don’t have a master project on hand to test. Please let us know how that works.