Running x-plane 9 on osx 10.6.8 for many years without problems, using CH basic yoke, mostly fly c172. Suddenly engine will not start or keep running. No failures set, engine running when opening program selected, fuel in tanks, mixture rich etc.... None of the A/C engine will start, or continue to run if initially running such as starting on final approach etc. I'm completely out of ideas!!! Reinstalled X-plane in a new folder but the same problem. Something somewhere must be set to disable all fuel flow? Help please!