since yesterday i've been doing a deep search through every forum and i haven't been able to find a solution to this; i've read about a lot of people having that black screen when they start episode 2 or the DLC, but mine's shows up at the moment i start the game.
I bought TWD through Steam and played for about 6 hours until i got to episode 3, after that i closed the game and never started again.
I'm running it on MacOS 10.9.3 Mavericks.
I have already tried to uninstall several times, change prefs.prop, delete saves, i've even deleted Steam totally and re-downloaded everything without Steam cloud, but it keeps on showing that black screen.
I've uploaded the trace generated by your support script and uploaded here:
Hope you can help me.