you need to download the update which is prompted at the start of the game
"please download the update for this game via windows live" (something along those lines)
after downloading this update, you still wont be able to save your game right away.
SO close the game (the right way, not alt+f4) and as soon as you do that, the installer will autostart and install the update. after that follow the onscreen instructions (also delete the dirt3 folder from the appData folder in c drive).
Also you need a high speed internet connection for the download to finish. It took me more than 1 hour to download the update. worst thing is, the update can only be downloaded ingame. no other way around it.
Hope you have the retail full version cause I don't think it has a crack etc. I bought this game for playing online and online play is quite awesome.