Client server mismatch

I'm really sick of this problem so i hope you guys can help me.
I had this since 1 week or something :

Everytime i connect to server it says awaiting gamestate adn then it pops to this error :

Client/Server Game mismatch : 'Enemy Territory/ET Pro"


I've reinstalled ET 6 times , didn't work
Then i Formatted and i reinstalled .. Didn't work

I just don't know what to do , pls help me