I've just bought a 2GB set of RAM from Corsair to add to my current 2GB of Corsair RAM. The two sets of sticks are identical in specs. (CM2X1024-8500C5D) But for some reason they are not working together. I've worked out that the RAM slots are fine, and all four sticks work fine as well. However I just can't get the computer to boot up when I mix the 'old' RAM with the new RAM. On the side of the new RAM sticks it reads: '2.10V ver5.1' On the old it reads: '2.10V ver4.1' But other than that, they are completely the same. Surely this small difference doesn't render these sets of sticks completely incompatible?