I'm having this same problem. I will get "out of memory" sometimes with only a single, clothed V4 and no scenery, yet i can have that same figure along with a complex scene with the same render settings and it will render fine in P7.  Even more odd is that if I look in the windows task manager I still have quite a bit of memory available. In p7 there are times where it is using close to a gb of ram during a render and it will finish, yet I'll get "out of memory" in p8 at 400-500mb ram usage.

I've also had the same thing happen where it will give that message after the render completes, while it is going back to the preview state. My drivers are up to date so I'm just stumped. It does seem to be a bug of some kind. I guess it's time to wait for the next update and hope it's fixed.