ON THE DATE MENTIONED, I WAS DRIVING AN ENTERPRISE RENTAL CAR, 2008 CHRYSLER SEBRING LX, FROM IDAHO FALLS, ID TO SALT LAKE CITY, UT. I WAS TRAVELING APPX. 73-75MPH WITH THE CRUISE CONTROL SET FOR THE LAST 50 MILES. I WAS APPROACHING ASEMI TRUCK/TRAILER AND TAPPED THE BRAKES TO DISENGAGE THE CRUISE CONTROL. AT THAT TIME THE CAR STARTED TO ACCELERATE, I TAPPED THE BRAKES TWO MORE TIMES TO TRY TO DISENGAGE THE CC AND THE CAR JUST CONTINUED TO ACCELERATE. AT THIS TIME I DECIDED I NEED TO TAKE A MORE AGGRESSIVE APPROACH AND STARTED SLAMMING ON THE BRAKES WHICH CAUSED ME TO LOSE CONTROL OF THE CAR AND STRIKE THE REAR END OF THE TRAILER. THAT CAUSED ME TO SPIN OUT OF CONTROL AND ENTER INTO THE CENTER MEDIAN OF THE I-15. I WAS ABLE TO GET THE CAR STOPPED AFTER THE WRECK. FOR WHATEVER REASON, I COULDN'T GET THE CC TO DISENGAGE AND IN FACT THE CC CAUSED THE VEHICLE TO SUDDENLY ACCELERATE. I HAD NO CONTROL OF THE SPEED OF THE CAR. THE BRAKES WERE REALLY NOT TOO EFFECTIVE IN SLOWING THE CAR WHILE IT WAS ACCELERATING. *TR