[John Benz]

Dead note, or dead string? If the entire string is dead (I'm assuming you've changed strings) it's likely a worn saddle or nut. If it's just one note, it could be a worn saddle, nut, or worn fret. Or, your action might be set too low. In any case, take the guitar to a reputable guitar store. They'll be able to tell you exactly what's wrong and offer advice on repair.