Weird stuff going on with the optimization

If the spikes happen from the beginning, and they disappear completely if you play on 32bit mode, sounds like some other program is messing with the game.

Have you checked this list to see if you have any of these programs running in the background? (click on the link to see the full list)

Paging @Albert for thoughts.

I will investigate the spikes when I got the time anyway, since many players complain of some type of leak after playing for several hours.