Anti-cheat authentication timed-out

I'm a player from China, and after today's update, I can't get into any server!
I played Sandstorm for one week and never seen such shit like this!
Every time I get in a server and player for 1 or 2 minutes, I will always be kicked out and there's a notice saying "anti-cheat authentication timed-out".
What the hell does this mean? I played Insurgency for 800 hours and never cheated.

Fuck this shit.

Use the "Verify of Integrity of game files" option und properties -> local files.
Steam redownloaded 2 files and so far so good.