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My TeXShop has been acting out: I haven't been able to open files with it. I was able occasionally to open document class files, but I had no luck whatsoever with beamer files. I can open and compile all the files using TeXMaker. I've tried reinstalling the entire MacTeX package twice but the problem persists (I'm using the latest TeXShop and the latest Sierra on Mac). Someone from comp.text.tex suggested that I need to find and remove TeXShop's configuration file, but I don't know how. Any help would be appreciated.