What version of the Nvidia drivers
are you using? There is a problem reported with the 196.75 versions so if you have them, you should revert back to the 196.21.
What resolution are you running the game at and what quality level are you using? If your running ultra, try lowering to very high to see if that helps.
I'm running a GTX 260 on win 7 64 bit and have never had a lock up.
One thing you can do to prevent the double launching is after you sign in and the screen goes black to switch to the game, just click your mouse on the black window to set the focus on the game. You have to be quick to do this but if you can get the click in, it should help. At least it has for me.