Changed Case and Now PC constantly restarts

Hey guys specs are as follows although I´m not sure they make a difference here as the PC worked before:

Thermaltake Toughpower 750W Modular
Intel I7 920
Gigabyte EX58 UD3R
Corsair Dominator DDR3 6GB
Gigabyte GTX 275
Thermaltake Element G
WD HDD 1TB

So the issue is that I had bought the PC is Australia and set it up there. All worked fine with no issues at all. Last month I had to come back and so I pulled everything out to take with me on the plane and then reassembled where I live in Spain with a new case.

This is where the issues start and Ive spent 2 days troubleshooting to no avail.

The PC turns on and then turns off again 3 secs later and repeats this until I turn the PSU off. When this happens:

All the case lights come on and I can modify lights and speed.
CPU, and GPU start up
HDD boots up

Once I got it to boot up and start booted up but I had no signal from the graphics card. This was when the card was not quite seated properly so I turned it off and screwed it in. Once this was done the same turn on/off issue returned.

Side note: I have the modular toughpower but left the module for SATA power for the HDD in Australia and am using a molex converter, could this be the issue? I dont think so but its worth covering that as well.

Any help would be great as Im running out of ideas.

Thanks all

Thanks for the quick response, Ive narrowed it down the GPU, if I take the grahics card out then the pc stays on. What should I look at barring checking another card as I do not have one available. Thanks again, don´t know what I do would do without PC forums!!

Update: I have no antistatic shield as I lost it in the move, could this be it?