Portal 2 has been running just fine on my computer for months, but today I can't even open it. I've already tried re-installing it, but I keep getting the same error. Does it have something to do with today's update?

Screen Shot 2015-10-10 at 12.31.41 PM.png

Same. Happens on Windows here. Don't have any fancy error dialogs, just closes right after the "Portal 2" splash screen.

Nobody even owns a steam controller, why does this update need to be pushed out to everybody.

Aparently it happened to everyone with a mac.

Okay. I found a workaround until valve fixes the update. If you opt into the beta for portal 2, the game will load. It doesn't appear to be any different from the game before the update.

I had mine working (with just the worst lag imaginable though) I am not sure what is going on.

I had to completely re-install the game to get it to work again. Silly Valve.