My PSU has started making a clicking noise when I boot, during use and when I shut down. It is a year old and a XFX Core Edition 850w
The problem which you have listed is similar to mine.
The reasons which I have found were:-
1)psu is not giving enough power to the system
2)full utilization of capacity at the time booting (creating a noise)
Try replacing it with the new one or if its in warranty just get it replaced with the model.
I have chosen Corsair 850w AX as my psu.