[Sensori]

Sounds like the game's copyprotection going into force. When you bought the game, did you get a manual with it? If not, it's pirated, and you should buy one from Shrapnel Games mefinks.

If it's not a pirated version, try reinstalling the game. The copyprotection can also affect people with actual bought version of the game if something gets corrupted.

Note that this info was in the FAQ. It's there for things like this.