Strange OC issue on LPUltraB DFI

I was able to hit all time high 230FSB at 1.8V because 1.7V seemed a bit unstable, with 1.8v it all seemed fine! the crispy sound wasn't there and I was able to ran 3dmark06 throughout the entire process but shortly after that my pc started acting weird again! first I lost network connection, then I said WThell I'll launch a game and it maked that crispy sound again!! why did it suddently went bad? I know I should had try rerun 3dmark again to see if it was diferent now. What do you think is going on and... can I past 1.6v on the chipset on this mobo without extra cooling for the chipset? and also if my PC was unstable as it was would I been able to ran 3dmark06 and if not then why I did it normally at first sight?