As per specifications on the processor and the Intel chipset, they both support ECC.
I would recommend contacting your motherboard manufacturer for possible BIOS update or more troubleshooting assistance.
Additionally, try testing the processor with our processor diagnostic tool
Thanks for your reply. I know it's not a compatibility problem, they all worked together for more than two years. I updated the bios and restored the defaults and the problem persists. Asus tech support hasn't been very helpful. They just tell me to swap out the parts one by one. I'll try the diagnostic tool and see what that tells me.