Haswell PC inconsistently coming out of hibernation?

I recently assembled a low-wattage PC. The GTX 750 TI only requires a 300w PSU, while I have a 360w Seasonic PSU with excellent professional reviews, and my PC shouldn't be drawing anywhere even close to 360w. I'd assume it would be fine. Full specs are here.
http://pcpartpicker.com/p/YB73gs

I've enabled the Asus EPU on my motherboard, set to auto. I've enabled C6 and C7 power states in the uefi bios, since my PSU is supposed to be Haswell certified. I have the PC set to sleep automatically after 30 minutes.

The problem is, sometimes my PC encounters an error trying to wake from hibernation, and has to reboot. I don't know why, and it doesn't happen every time. When it does wake correctly, it takes 20-30 seconds to wake, which is unexpected as well.

Updating the Bios to the latest revision didn't fix the problem. Windows 7 is fully updated. CPU idles at 30c and maxes at 58c under Prime95. Board idles at 32c.

All the parts are completely new, and I haven't encountered problems aside from this one.
Does anyone know what the issue might be, or have ideas how to fix it?