Black Ops Zombies Nuke (ps3/360 only)?

ok the month the ps3 was down i played blackops on my 360 and found the first difference.... the nuke. on the ps3 when you grab the nuke, the zombies cannot hurt you for a short time (even if surrounded). but on the 360 when you grab the nuke, the zombies can still kill you before the nuke manages to kill the zombies. why is this?