mrandersen:
I think you have to make those two variables 'volatile' as I added to your code above. Give it a try and report back.
http://arduino.cc/en/Reference/VolatileLefty
I tried this but both variables are still printing as the same number.
Well maybe the interrupts are coming faster then you think. Try using micros():
timeStarted = micros();
timeEnded = micros();
Lefty