I am also having issues getting the beta to load.
I click launch in steam, the splash screen appears, then it just crashes back to desktop as if it had never been launched without even an error message.
And yes I am using windows 7 64 bit with the latest drivers (as of today).
I have reinstalled the game to see if that helps.
I am unsure if I having a similar issue to the OP, but I could be.