THE FLIGHT HAD BEEN AIRBORNE FOR APRX 38 MINS WHEN THE PILOT BEGAN EXPERIENCING COMMUNICATION PROBLEMS. NINE MINUTES LATER THE PILOT REPORTED 'INSTRUMENT PROBLEMS' AND BEGAN TO RECEIVE RADAR VECTORS TO A LANDING. 15 MINUTES LATER SHE DECLARED AN EMERGENCY AND SAID HER MAG COMPASS AND DIRECTIONAL GYRO HAD MALFUNCTIONED AND BEGAN RECEIVING NO GYRO RADAR VECTORS AT 1000 FEET MSL. AFTER RECEIVING THREE NO GYRO TURNS SHE WAS INSTRUCTED TO 'STOP TURN.' TWENTY FIVE SECONDS LATER SHE SAID 'I'M, I'M STARTING TO SPIN.' NO FURTHER TRANSMISSIONS WERE RECEIVED. THE AIRCRAFT IMPACTED APRX 3 MILES WEST OF THE INTENDED LANDING AIRPORT. AN EXAMINATION OF THE ATTITUDE INDICATOR, THE DIRECTIONAL GYRO, BOTH VACUUM PUMPS AND RELATED COMPONENTS INDICATED THAT THEY WERE FUNCTIONING UPON IMPACT. THE ACCURACY OF THE INSTRUMENT INDICATIONS COULD NOT BE DETERMINED HOWEVER, DUE TO IMPACT DAMAGE. AIRCRAFT LOGS REVEALED NO PREVIOUS INSTRUMENT SYSTEM WRITE-UPS.