how do i tell if its time to RMA my A8NSLI-Premium

[Cow Hunter]

currently running an A8NSLI-premium board mentioned in my signature and i have had all sorts of problems that i was getting ready to blame on my ram. for starters i have been having major stability issues with the overclock mentioned in my sig, lately 2 or 3 crashes a day, and last week i realized my ram would fail memtest at and even slightly below its specified 250mhz. so while waiting to get replacement ram, my video card started crashing to desktop and not letting me restart any 3d games until i restarted my computer. at this point i was confused since my graphics card wasnt overclocked, so i removed my CPU overclock and started running everything at stock. now today the first day after running at stock i crashed(computer just restarted itself). so anyway i just went to put in my replacement 2x512 corsair DDR400 ram in so i could RMA my G-Skill. well i booted into the bios and told it to do default ram settings but it tried to run it at 200mhz, when i manually changed it to 400mhz it failed to boot and i had to clear the CMOS. right now its running my ram at a frequency of 200mhz DDR speed, so basically at 100mhz which is really sad.

So right now i am wondering is it my Motherboard, do i have a faulty powersupply thats causing the random restarts, or is it something else. the fact that my ram fails memtest at 250mhz wouldnt result from a faulty powersupply i am sure. well anyway i will have to wait until this weekend so i can run Memtest on my G-skill ram in my other computer to see if there is even a problem with the ram at all, if my A7N8X can even reach close to 250mhz which i doubt it will .

Well anyone got some suggestions or recomendations.