ocz not work on nf7 HELP!!!

I'm runnin 512mb ocz 512mb rev 3.2 2700 on my nfz s 1.2 and it doesn't boot up. i stick in some old 2700 256mb and it worksd.....
so i tried my old memory and the ocz and it works in dual mode .... what's goin on?
plz i need help

raise your voltage. The OCZ sometimes needs more voltage to run, if that doesn't work RMA it.