How does it handle Linx @ max mem? 5 hours Prime95 is reasonably stable, but it's not uncommon for crashes to occur after that point. Are you working up slowly from a fully tested confirmed stable point?

People often report instability after flashing to a new BIOS; did you set all settings again manually or load the preset saved settings from the old BIOS? Apart from potential settings set incorrectly when loading saved settings from an OC profile, sometimes real voltages can be different despite the same BIOS set voltage being selected. As you are getting instability with the latest BIOS, when all settings are set manually again, have you confirmed all the voltages are what they used to be?