I looked and it seems this is more of a problem for MAC users. I have Windows 8. Game worked just fine couple days ago when I still had Windows 7. All my other Steam games work fine, not L4D2.
This sucks I've been playing a lot and now I can't. I tried verifying files. I refuse to re-install I just want to fix the game. If I can fix POS Origin to not have to re-download BF3 surely I can for Steam... 700kbps would take too long.