I have bought a ram upgrade kit. (2x2gb ddr2 800mhz, icidu si-707216) When I put in just one of the two cards in any of the two slots, there is no problem at all. The PC boots normally and everything works fine. Now, when I put both of the cards in my mobo, I get a black screen. Nothing happens. I've tried one of the two cards in combination with other spare cards I had, but the same happens, absolutely nothing.