UI自动化在iOS5模拟器上运行良好，但在iOS6和iOS7上就不行了

It seems like iOS5 simulator is not supported on Mavericks. That was the only simulator that worked for me, and I have a bunch of tests in UI Automation. iOS6 and iOS7 simulator takes 2-5 times longer to load (about 30-50 seconds), and my guess is that instruments times out before the sim is started. I get a "An error occurred while trying to run the script." however - the error message appears after 1 minute. I have a MacBook Air 1.4 Ghz with 2GB of memory. Quite strange that iOS5 worked so snappy and all other simualtors so incredibly slow. Any ideas?It seems like iOS5 simulator is not supported o