Crap.
Built my PC yesterday and it worked flawlessly.. about an hour. The PC suddenly shut down and wouldn't start again. Just a small blink from the power light when I pressed the power button. Replaced the PSU with my old one and everything worked fine. Well, "tough luck" I said, "need to RMA that PSU and get a new one, but oh well, I'll just use my old PSU until I get a replacement". Then, after a couple of reboots I couldn't get into windows anymore and when I went to BIOS there were no hard drives listed anymore. Loaded the default bios settings and booted, and now the the motherboard recognized the drives and I could log in to windows again. They were gone again after the next reboot.