You can't start FS? ???
Does it load the splash screen and then it freezes and won't respond?
If it does, follow these steps:
1. Start the task manager
2. Check your CPU Usage at the bottom of the window
3. Check and see if FS is responding
If your CPU usage is @ 100% then there's someting wrong. If it says the FS isn't responding, that's OK, because after awhile it loads anyway.
If you have 100% usage AND no response, you should delete your fs9.cfg file.
Next time you start the sim, FS9 will make a new one...
You'll have to reset your preferences, but that's better than not having the game run at all...

I had the same problem.
Hope it works!