should be one of the first options in the AI tweak menu in bios, set "overclock tuner" to manual and then make sure the option that appears below it (BCLK/PEG Frequency) is set to 100.0
you can also set it to "X.M.P." and then set the same frequency to 100.0, that XMP option should automatically adjust all timings for your RAM to optimal values but I haven't tested that myself yet, I rather do everything manually
---wait OK then it is probably because of the automatic overclocking ... well I've used that before as well for fun but not really to run 24/7 ... voltage settings are usually quite high when doing that and it adjusts BCLK/PEG Frequency as well for no real reason. I would just go with the settings that the automatic overclock settings found, then enter them yourself in the bios with a BCLK of 100 (which will make you lose about 150 mhz of CPU speed).
If you read a couple of Sandy Bridge overclocking guides they'll all tell you to keep it simple, set the BCLK to 100, enter memory settings manually or using the XMP, then up the CPU multiplier till it gets unstable, up the voltage to get over instability, up CPU multiplier again, voltage again and so on until you get to ~1.35v voltage which is the recommended safe maximum on aircooling
the whole higher BCLK thing is nice for suicide-run-benchmarking, but will gain you hardly anything more but potential instability and other headaches for 24/7 usage