cpu overheat, mobo NB & mosfet overheat , vcore low , vcore fluctuation , unstable voltage supply , electrostatic interference , electromagnetic interference, improper multitasking during load... blar blar blar

many reasons, have to find out yourself 

edited: of coz, unstable oc is included 

it does

increasing NB voltage will help the stability of the OC system

simply the chipset need more voltage to coop up with the proc

do correct me if i'm wrong

looking for a better cooler first. now still on stock, damn hot when i try to oc higher.