I have a late 2007 MacBook 2.2ghz. I want to upgrade ram to 4gb. Will two 2gb 800mhz ddr2 work or should I use 2bg 667mhz ddr2? I am looking at the Kingston brand. Will these work. I've read reports on problems booting up with a pait or 800mhz ddr2 ram. What will be the optimum ram setup for this particular MacBook?