Well - moving it to 32-bit has stopped it crashing. It has also made the performance when it doesn't crash even worse. As others have commented, when reducing SSAO makes no perceptible difference to performance, there is something seriously wrong. I may not have the fastest machine on the block, but it was way over both the supplied specifications. I read some complaining about 18fps, I doubt I'm getting more than 3 - i.e. unplayable, and now it's everywhere, at least in Europolis, and thats with everything disabled/on low The main screen from where options are selected was fine before - now even that is a laggy piece of garbage. I'm going to have one more go on a W7 VM, then consign this to the trash.
Regarding the SSAO reduction you're mentioning, it doesn't mean something is wrong:
If reducing SSAO does nothing (framerate or visually), it just means that SSAO is not used in that specific area/scene/camera of the game. There are some cameras/scenes that applies SSAO, and some that don't. Turning SSAO off (menu option) just makes sure that SSAO is turned off where it is supposed to be used.
Are you playing on Steam? Are you sure it has been updated?
It's at least really weird that you're experiencing worse framerates than before, as the performance fixes implemented in the patch are mainly of a "tone stuff down"-nature, and shouldn't result in a worse experience.