I have an Asus P5N-E SLI motherboard (latest bios). I have 4 GB of of OCZ SLI PC-6400 ram (4x 1GB OCZ2N800SR1G). Whenever I even enable the SLI memory setting (enabled 0% overclock), the system hangs on boot. If I disable the SLI memory settings, everything is fine. I ran memtest and ram is stable. Any ideas.
It probably means the memory modules are not stable at that speed because enabling SLI memory setting increases the clock speed IIRC. Try increasing the voltage for your memory or increase the memory timings.