Led lenser head torch

I have a led lenser seo3 head torch. All of a sudden it stopped working. The batteries are brand new Duracell. When I push the power button I get either a single quick flash, or nothing at all. I have cleaned all the terminals etc, and double checked the batteries. The most it has stayed on was for 15 secs, before going off again. My common sense tells me it's the same symptoms you'd get on any small battery device with a loose connection somewhere? Can anyone help me with a suggestion as to what is wrong, and how to maybe fix it. It is out of warranty. Thankyou.