I asked this same question last year, but want to ask again to see if anyone knows how to fix it since I haven't found any solutions. All that happens is once I install the game, I click on play as usual, but when I do that, an update pops up saying Rainbow Six Vegas GameUpdate. There's two lines, and the top is the one with small green squares progressing to the right which indicates that there's a patch installing, but once it's done it quits out.  
 
After a couple of seconds of loading as if the game were to start, and the little gamer icon down at the bottom right (where it says VIEW FRIENDS) is green for those few second, then all of a sudden it goes back to blue. Nothing happens at all. And it also says LAST PLAYED TODAY where you click to play the game. It's been frustrating, and I'd like to see if it runs better than it originally did. I hope the details I described were clear enough to all of you and if you find me a solution, thank you very much.