Hello! I was having the same problem, with the steam window popping up saying "preparing for launch", and so I looked up this troubleshooting thread. However, I didn't exit out the the "prepare for launch" window when I did, so it must have been continuing it's loading or whatever. In the time it took me to read all these comments, though, the window suddenly went away and the game started. I don't know if it's my computer's fault and its just slow at loading, or it was having the same problem everyone else seems to be having, but in my case, it was solved simply by waiting it out. Mabye after updates of the game it needs a little time to prepare or something... Mabye you could try just starting the game to where the "preparing for launch" window comes up and let it sit for 5-10 minutes. Hopefully that will solve the problem. I wish you luck!