Frequent post-patch crashes/reboots from game

[SQB]

Gah, I'm really frustrated!
Before patch: 25fps (reasonable) over london, barely any stutters.
After patch: Well, the game doesn't start, just has the steam "opening game" box and then "launcher has stopped working."

I don't know what to do, all files validated successfully, I re-installed, and It didn't install anything in my documents, which I thought was odd so I checked all files again, again it said all files were fine.

How can all files be fine if the game doesn't run...?

If anyone has any tips or suggestions it would be MUCH appreciated.