So unfortunately I had a project on my timeline and I clicked Ignore - now I can't close FCPx - any suggestions? Tried to force quit and it won't let me do that says it's still loading... I do have a back-up of the project.
If the usual Cmd-Opt-Escape version of Force Quit does not work, try force quitting from Activity Monitor.
Activity Monitor is in the Utilities folder inside the Applications folder. Open it, select the line for FCP and click the "Quit Process" button. In the dialog that appears choose Force Quit. This seems to be more decisive and should work.