Surprisingly I could not find this with a search. Some, not all, Excel files created by myself will not let me save them because they are read only. I have unchecked everything in the Trust Center. I found references to the "Microsoft Office Button", which leads to Backstage, but cannot find it! And the description implies it is nothing more then the Options Trust Center GUI anyway. I either get "read only" or "Cannot save to this location, do you want to save in your Documents?"
uSoft just really makes it hard to manage files when I created them, and am the only user of this machine in my home office.