WHILE EN ROUTE ON A X-COUNTRY FLT, THE ENG SUDDENLY LOST POWER. THE PLT INITIATED A FORCED LANDING IN A PLOWED FIELD, BUT THE ACFT ENCOUNTERED A RUT & NOSED OVER. IT WAS REMOVED TO A FACILITY FOR AN INSPN OF THE ENG & PREPARATION FOR A TEST RUN. THE ENG WAS STARTED & WAS OPERD FOR SVRL MIN AT VARYING POWER SETTINGS WITH NO ABNORMALITIES NOTED. THE TEMP & DEW POINT WERE 44 & 32 DEG, RESPECTIVELY. ACCORDING TO CARB ICING CHARTS, CONDITIONS WERE CONDUCIVE FOR CARB ICING.