Hey Everyone,
You will find that if you have updated to OS X Mavericks (currently BETA 13/05/13) the iOS Simulator will not activate from the Flash Builder IDE. FB will prompt to saying you need to enable assistive devices but Mavericks has removed this option from the Universal Access option in the system preferences.
Here is the work around:
Activate System Events:
System Preferences > Security & Privacy > Privacy > Accessibility > Tick System Evenh
There is no need to restart Flash Builder the simulator should now just work fine.
Hope that helps prevent a lost few minutes on the old google machine.