When i played the Korean Beta, myself and a lot of other people experienced crashes and random reboots. This was occuring because of the high detaild effects were either turned too high or on. Im not sure if they resolved this with some updates etc, but heres how to resolve it once you play:
Open up the Client and click on "setup" and lower the indicated setting.
Hopefully we wont have to do this, and enjoy the nice high detail effects, but heres how to ammend it, happy gaming.