You need to step back and have a really good read up on some guides.
I tend to start at the stock voltage then bump up the fsb bit by bit until it becomes unstable, then add a little voltage and again bump the fsb up until it becomes unstabe. This should get you the lowest possible voltage for your overclock.
Watch the ram speed and keep it just under stock speeds on stock voltage while you're oc'ing, that should discount it being a problem.
Make sure the PCI speed is...