when I launch lightroom it tells me to "quit the other copy of lightroom before trying to launch." I don't have another copy running. What do I do?
That is a new message that I haven't heard stated just that way. This usually indicates that Lightroom has not shut down normally, and has left a file that makes Lightroom think it is already running when you try to start it again. Using Windows Explorer or Finder (depending on your operating system) go to the folder that contains your Lightroom catalog. In that folder you should find a folder with the same name as your catalog, but with the .lock extension. You need to delete that lock file, and then Lightroom should start normally.