Re: RAM Issue
Make sure it's running at no faster than 667mhz, the max allowed by this board. The board can support up to 4GB, so you're within range. The sticks are fine, as he tested them individually, the problem is probably in the BIOS. I agree that it isn't running Dual Channel. Have you given any of the newer drivers a try to see if maybe there's an issue there? If it's just back and running, perhaps it doesn't have the most up to date drivers. When this came out, 1GB of RAM was baller status. Afterall, this came out even before the hyperthreaded single core P4 was out.
If it's a physical and not a intellectual problem (BIOS or driver), it might be that the second DIMM slot is malfunctioning. A bad connection of some sort. It seems less likely, but try taking a computer duster can and just giving it a good cleaning inside both DIMMS. Couldn't hurt.
Desktop: AMD Phenom II 840 X4 @ 3.7Ghz // Asus Sabertooth 990FX // CM HAF 932 // XFX HD 5770 // 8GB Corsair Vengeance @1600 + 8GB G.skill Sniper @ 1600mhz (C9) // Cooler Master 600W // Zalman CNPS9900 // Sidewinder x8
Laptop: Dell Vostro 3555 // AMD A6-3400 1.4Ghz x4 w/ 6520 // 500GB HDD // 4GB Ram upgrading to 8GB soon // Backlit Spillproof Keyboard