steam games and issues with with wireless xbox 360 controllers

I'm pretty pissed, once more my xbox 360 controller won't be recognized by a steam game anymore, which used to work prefectly fine 2 days ago. this time I'm extremely pissed as I spent 24h on the game, being at the final battle and now this. I experienced it with other steam games also, this is the 3rd time the controller just doesn't work anymore, out of the blue (the games have not been updated in steam or something). Anyone had similar experiences with games on steam? What could this be, and is there any turnaround (and no, I'm not going to use the keyboard for those games, especially not in the one I used to play 24h with controllers)???