I have tried all of the "fixes" and every time I get the game working another Steam update comes out and I have to start all over. I didn't change anything in my working game from three days ago, but today (after an update was applied), it won't start. I have other games to play so that is what I will do until I feel like investing another couple of hours of my time debugging and getting the game to work. Without any modding tools and with these crashes the game doesn't have much value to me. it is a shame because (when it works) the game is quite enjoyable, and the members of this forum have done an incredible amount of great stuff especially considering you had to create your own tools. I consult on IT projects for a living and whenever I run into a problem where there are "quite a few fixes" to try, it means the root cause has not been found (or admitted to). Hats off to the members of the forum and you, IdolNinja for all you have done. I hope Steam and Volition put forth half as much effort to make the games useable..The "app is already running" error actually has quite a few fixes you can try which I've outlined in the Troubleshooting FAQ
http://steamcommunity.com/app/206420/discussions/0/846965705311116184/