Hi,
I'm using 4 x 512MB of Crucial Ballistix DDR400 on the A8N-SLI-D with no problems.
Lore
System: AMD64 FX55, Asus A8N-SLI-Deluxe, 2 GB (4x512) Crucial Ballistix DDR400, 1 Gigabyte 6600 GT PCI-X graphics card, Thermalright XP-120 heatsink w. 120mm Panaflo M1A Fan, Microcool North...