Power spikes? Rig rebooted due to PSU protection? Tell me which one would do that instead of just shut down PSU itself:
OVP (Over Voltage Protection)
UVP (Under Voltage Protection)
OCP (Over Current Protection)
OPP (Over Power Protection)
and SCP (Short Circuit Protection)
Any of the "Over" stuff. Don't know that much to be able to tell exactly.