If there's an electric motor shop close by, have them check it out. Unless you can smell anything like burning rubber or insulation and the motor shaft spins freely and quietly (no bad bearings), I would suspect the capacitor. Try changing the speed setting (use another tap on the motor (there are usually 2 to 3 speeds) and see if it runs. If it does run, more likely a bad motor winding. If it doesn't run, more likely the capacitor.