I have several PC based camera dvrs that have been locking up on me. They are all ASUS z87k, I7 3.4, 16Gb, Samsung 840 Pro SSD for OS Drive, 6TB of WD Black for storage. It seems to be about 1 out of 10 of my builds this year are locking up without any event log trail of failures other than when my client holds the power button in to reboot the machine. From there they run anywhere from 12-24 hours before freezing.