0.) Log into XFires forums with your xfire username/password find the thread if theres one and shout loudly for them to stop breaking it!!!!! (Optional but recommended)
1.) Start XFire and log in
3.) Click Raven Shield in the game list and check the 'Disable X-Fire in game' button.
4.) Click Accept.
XFire should now let you play RvS without crashing the game. The price, you won't get the In-Game features from XFire.
Yes XFire is rubbish -- let's complain tot he company til they are sick of us!