How long are you running Memtest and Orthos?
What is your full specs and the settings you are using, maybe I can see something off causing your Random reboots
Sorry, I reply as I read. I see you narrowed it down!!!
I will ask My Contacts about this for you, if I do not reply back to here or PM you within a few days please PM me to remind me to see what they have replied to me about this.
Email has been sent to my Contact, I'll keep you informed