As soon as I open it up, it closes after it logs in. I have reinstalled steam, SK, updated my drivers, nothing happens. When I verify the integrity of the game cache, it says 13 files failed to validate (like other posts in this subforum) and I still can't play.
I'm pretty sure you're referring to this thread.
Did you attempt deleting the steam folder as well? (And still get the 13 files failing to validate?)
Although now I have another trick to attempt:
Does the standalone client work? (dl via this link, which you get directed to when clicking "play now" on the main page while not logged into steam for the forums)
If that works, does copying the folder from the standalone client into the steam folder fix the problem?