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.
I would check the ram qvl listing for your board, or write asrock using their tech support form. I doubt the ram is bad. Give them 24 hours to respond. You may need a bios flash, but I don't recommend it until you contact them.
YEs, if it's not too late I think I know what the problem is. Your RAM is rated at 800MHz but that's only in single channel mode. It needs to be dropped down to say 667MHz for dual channel. What you need to do is boot with one stick, adjust the RAM speed to 667 in the BIOS, then add the second stick and it'll boot fine. This has been reported for the cheap Patriot RAM sticks from Newegg among others, let me know how you get along.