Yes United 585 occurred before US Air 427. There was another event (can't remember the airline) near Charlotte, NC just after the US Air crash and they were successful in recovering the aircraft. Basically, the primary rudder servo valve jammed in the full deflected position (without either pilot commanding full rudder deflection). The "work around" was to cycle the servo valve breaker which reset the valve. I believe that they also had a way of using the secondary valve, but I'm not a mechanic, either.
Once this was discovered, Boeing replaced all servo valves on the B737 (all models up to that time) with a newly designed servo. Since this took time to do (I think I remember hearing that most were retrofitted with the new servo by early 2000), pilots had to go through additional training on how to recover from this situation if it ever arose. I do not recall any incidents in the U.S. after the third incident involving the B737.