I just ran several tests. It seems like everthing works fine with either one of the RAMs but not both. Both RAM works fine on both DIMM1 and DIMM2 seperately, which I assume there's nothing wrong with the slots. I don't know what situation this would be. But there shouldn't be incompatibility issue going on here as I followed Crucials instructions. I have a hunch that it's the PSU. I remember I dropped my case (fortunately without the harddrive in) when moving to another apartment. Or is it the Motherboard? Please give me more hints. Thanks.