Out of the blue not that long ago, all of my keyboard shortcuts stopped working -- the new ones I created, as well as the ones that come with the program. I tried locating the keyboardshortcuts.xml file and deleting it, replacing it with an older version, re-importing it in the options menu, and importing an older version's xml file. I tried deleting the shortcuts within the program and reassigning the letters. I tried repairing and reinstalling Revit.