Hey man! Finally found the route cause of this issue.
It seems you're running a 32bit OS, we can't support that as UPDATE 6 swallowed a whooping 5.5Gb RAM (limit on 32bit is 3.5Gb per app roughly,) UPDATE 7 has been optimised and chews around 2Gb RAM now but a 32bit build is still a lot slower so we can't put it out there.
How much RAM do you have in your machine? You should think about going 64bit, not just to play SS but the OS will be a lot snappier in general....
Also, we'll be updating the Humble builds to UPDATE 7 later this week, sorry for the delay!