TechPowerUp writes NVIDIA now admits that users may experience data corruption issues on nForce 790i chipset based motherbords when overclocking:
NVIDIA has received reports of data corruption when using certain high speed memory and overclocking the front side bus. Our engineers are currently investigating this issue and as soon as we have more information, we will provide an update to this knowledge base article.
A workaround isn't available (yet) so nForce 790i users are advised to keep their processors running at stock speed. This is a pretty big screwup considering most buyers of these chipsets are people who want to overclock their CPU bigtime.