I don't know if this will help you, man, but it helps me on my end.
1) Do
exactly what raymondlee said in his post.
2) I always, and I mean ALWAYS, have to right click the FPSC icon and run the program as an administrator in order to use it.
I tried just clicking on it as normal, and when I was creating, testing, and building my levels, I experienced most of what you're experiencing now.
Sometimes, your computer may force you to run certain programs as an administrator before you can use it.
Try it. It may help. It helped me...and to think I was uninstalling, rebooting, recovering, reinstalling, etc. etc. etc. and I just needed to run the program (v1.18) as an administrator
Oh, and I started with v1.0...so yes, upgrading to the latest version will help out a lot if you have certain model packs like some people have said on here.
GAME ON!!!
--King Cobra