I saw you asked for Matt's advice on another thread. I guess you still haven't figured it out. Well, I've really don't have anything else to point you to. It's more of a hardware problem than a Linux problem. My advice from this point would be the same as Matt's ... to try to remove and then install ram, video cards or other removable pieces of hardware until you can find the one that is causing the problem. When one of my 4 new sticks of RAM caused the POST to fail, I inserted one at a time into the primary RAM slot and booted one at a time until the offending stick was discovered. In my case, there were no beeps, just the absense of a motherboard POST.

Other things to look at: Make sure there is nothing on the motherboard that could be shorting something. Might take a flashlight and a magnifying glass, but, make sure there's nothing resting on the motherboard that could have been left behind when removing and instralling the RAM. A screw that was dropped that wound up in a hidden place etc.

Reseat graphics card, remove and reseat all connections, look at connections around RAM slots ... could you have pressed too hard or not completely seated the RAM.

Things like this drive me crazy when they happen to me, but, after cursing and throwing a few things, I'll start from scratch (like I was building the computer from scratch) and analytically go over every step rebuilding it until I work it out. Without the hardware in front of me, it's hard to spot what's going wrong.