Machine blowing plug fuse.

[hanluc]

I have a Corsair 1000w PSU running a 3770k, woke up this morning to find the machine dead. The 3 amp plug fuse had blown going to the PSU, so I tried another kettle lead and it immediately blew that fuse.
What would be the diagnosis here?, I know the obvious choice would be the PSU but is it possible that there a a short the the Mobo? though I would have thought that the PSU would have shut down before blowing the fuse if that were case, but I don't know.

 

[hanluc]

OK point taken, but I was drawing around 400w max, and as I said it immediately blows the fuse so it's not that.

Edit

It's mildly OC'd to 4.1Ghz and it has a 570 in it.
It doesn't blow the fuse on boot, it blows it the moment I switch the PSU on, the green light on the MB flashes on for a split second then dies. I suppose the thing to do is disconnect it from MB then try it. Work know so I'll try that later.