Hello everyone, i'm joining the discussion as well: my sistem started rebooting randomly after updating to u5 a few days after it's release. At first i reverted u4, and the reboots disappeared. After 1 week they came back. I changed motherboard and for another week everything was fine so i decided to update again to U5. But reboots came back. This morning i woke up to a nightmare: i received 12 emails from the NAS with unauthorized reboots. The machine is basically hanging everytime it starts and i have no way to do anything. I'm running a memtest just to be sure everything is fine but it is weird to say the least.
Xeon e3-1231v3
Asrock e3c224d4i-14s
16GB DDR3 ECC
6x3TB WD RED
Seasonic 450W
2x USB 8GB (mirrored boot drive)