Upgraded to SLI, PSU now clicking. Help!

[Ashneo]

I built a new pc around 2 months ago. Everything was running fine. I bought another gfx card to upgrade to SLI and fitted it today. Now when under load in games the PSU makes a loud clicking sound.
Anyone have any ideas what it could be? As said, it's 2 months old so everything is within warranty... is it likely to be a faulty psu?

Psu - Super Flower Golden Green HX 750W "80 Plus Gold"
Semi-Modular Power Supply

Gfx - Asus 970gtx

Thanks in advance.

 

[Ashneo]

It's not the fan making the sound, i have just removed my extra Gfx card and the PSU is completely silent again with load. Think i will just ring OCUK tomorrow morning and see what they say / get a replacement. PSU going wrong scare me