Double check to make sure that your new RAM is the correct speed for your computer. Your Mac uses PC3-8500 RAM. You may have bought faster, newer RAM, such as PC3-12800. This RAM is technically backwards compatible with your computer, but it forces the bus to run at the faster speed, which it can't do. I'm having trouble finding the Apple support article about this, but it works like this: The bus can only run at the 1067 MHz speed of the RAM it was designed for. The computer will only run at the speed of the ''slowest'' RAM module installed. If you have PC3-8500 RAM in both slots, that's great, that's what the computer was designed for. But if you put PC3-12800 RAM in both of the slots, the bus will try to run at the speed of that faster RAM, which it can't do. With one slow RAM module in one slot, and one fast one in the other slot, the bus will run at the speed of the slower one, which it's supposed to, and then slow down the faster RAM so that it can also work (this is currently how I'm running my 2009 white MacBook).
Pretty sure it should give off some warnings though, so it's weird that it's not.