Alright sorry that I have been really stubborn about doing the demo try. It's just that I had a perfectly fine, working version of X-Plane, and now, noooo! So, I downloaded the demo, no crashes. I am now convinced that this isn't a Lion problem. What's the next step? I have already added and subtracted plugins one by one, problem aircraft one by one. Would the log.txt from the demo be of help? I compared them and there was nothing significantly different. Cheers