I got TWD a while ago via Steam (Mac version) and played it all. Then, I bought the 400 Days DLC in August and started playing it bit by bit (well, I haven't finished it yet...). However, two weeks ago, the game suddenly crashed when I was playing (and finally getting to the last story of the DLC !) without reason. Each time I start it since that day, the game refuses to launch and only show a black screen, with no mouse. I tried to delete and reinstall the game, it didn't work. I deleted the prefs file, and I got a black screen again.
I ran the data support program, here it is : https://mega.co.nz/#!zhIBGLLa!YFlJXyKvv32sSpmMK-dR6AvgdgVM-BpinDuqaRvlPvI
Even if my configuration is quite low to run the game, it still worked very well for several months, so I don't think that's the problem.
Thank you for your future help ;)