Have you verified that the BIOS is properly setting your memory settings? By updating the BIOS, the XMP profiles may have changed slightly. So, you may need to set your timings manually. Note, never update your BIOS while your motherboard has overclocks set on it. Use one stick of memory, set your motherboard settings to default, update your BIOS, reset your system (usually F10, Save and Exit), and then check/adjust your new settings for your hardware.