The colours should give you a clue. Your board most likely supports dual-channel DiMMs. That's not to say that your current DiMMs won't work (though a look at the Crucial memory selector to check specs would be wise). I suspect that by adding non-matched DiMMs to more than a couple of slots is causing the problem. If the modules are spread across both the yellow and blue slots, the motherboard will try to treat them as dual-channel, in which it splits data across them. If you keep only one paired bank full and leave the other side empty, that should work. Hope that helps.