But why did it freeze during the game? Something cannot handle high CPU frequencies because of a low voltage?
Right. The voltage was probably a bit low for the load it was under and it crashed. I'm not familiar with Asus's software, so I can't say how it achieves the overclock and what settings it turns on/off in order to get there so I can't offer any solid advice on what other BIOS settings should be changed to get things more stable. I can tell you that VDroop should be set to low/minimum though and PLL overvolt should probably be on with clocks that high.