If you tried it all and your game still locks and freezes. Follow the directions of the OP in this thread. Good luck!

http://forums.steampowered.com/forums/showthread.php?t=2165193

Can you tell me this please , So you just add +jobs_numThreads 0 to your steam launch options , Enable AI and play ? Or disable AI and play?
Also do i need to start a new game?

Enable Catalyst AI as well or you will get the patchwork quilt effect textures. I would start a new game too. Usually once one of mine gets messed up it keeps losing textures until it crashes or won't save without crashing to desktop.