Not at all:(

OK.

Have you changed anything in the Conf.ini file?

Have you modded your game?

Do you have multiple installs?

Varyfy the integrety of the game cache in steam. Goto Steam Library, Right click the game, select properties. Click the Local Files tab, click veryfy integrety of the game cache.

Ihave changed nothing in the game.I have done you told me to do and i thought you have found the solution because steam found 36 uncorrect files and downloaded them ( i also made a defragmentation), but it is the same: impossible to be connected 15 minutes later (then i stop because i don't thing something else will happen).