Game will no longer launch since update 126.96.36.199
To resolve this issue follow the steps below:
- Right click on the game from your 'Game' list and select 'Properties'.
- From the 'Properties' window select the 'Local Files' tab and click on 'Verify integrity of game cache..'.
During this process Steam may need to retrieve some of your game files again, once complete the game should now be working again.