HOW I FIXED MY PORTAL 2 (on a Mac)

[tiger]

I trashed icons for it in Finder & Applications. I trashed Steam icons also, but not files unique to my Mac that saved my progress halfway thru the game. With everything gone, I inserted my store-bought DVD and loaded the game all over again from scratch. Don't mistake the letter "O" for the number zero "0" in the Product Code. Let Steam do all its automatic updates. It worked. I'm right where I left off and I don't have to begin at the beginning. Good luck!