That nylon disk is a great way to hide a hellacious soldering job!
Have you tried gripping the top of the reflector (as shown in your first pic) and unscrewing the entire drop-in from the head? Once you have the drop-in out you should be able to unsolder or grind off the solder holding the driver into the pill and pop the driver. Once that is exposed you might find that a wire from the driver to the LEDs is loose or a component on the board is fried/burnt. Have you contacted the seller before doing this process?
It's possible that one or more of the leads to (or from) the LEDs has been guillotined during assembly.
I've seen several multi-LED torches now with that problem. The bottom of the reflector, or the body pass-through (depending on torch) has a sharp edge - during assembly, the wiring is twisted across the sharp edge.
The light may even work initially, then fail after just a short while - or it may arrive DOA, as in your case.
Further examination will require complete dismantling of the torch, so time to break out the soldering iron, and some de-soldering braid.....
I thought my soldering was pretty ropey, but I'm feeling a lot better about myself after seeing this ;)
I did try that, but I couldn't get it to budge (I was trying to be gentle though as I wasn't sure if it was supposed to unscrew). Having just tried again, either I'm weaker than I thought or it doesn't want to move.
I've not contacted the seller (DealExtreme), I was hoping to DIY fix it rather than go through their painful returns process. But needs must I guess, perhaps need to make a decision now before I start unsoldering things :)
So I made some progress in that I realised there's actually another part of the head of the light which un-screws. Unscrewing this has given me access to the driver itself.
In doing that, the problem is obvious - the board has been broken when the head has been screwed back on, it looks like a pretty crappy design.
Here's the section with the driver, showing how it was as I opened it: http://t.co/NBa46cKY
And here's after de-soldering the remaining leg holding the two pieces of the driver together: http://t.co/pv6TIp6P
I don't see how I can fix this myself as it looks like the copper tracks on the board are now missing, hence re-soldering it would not work, am I right?
..just me or the TR-J12 with LED's re-wired in series, equipped with either http://www.kaidomain.com/product/details.S020077 (cheap, but as it supports only 4 LEDs, center one would have to be disabled) or something like TaskLED Hyperboost (more expensive, but way more functional), and three A123 LiFePO4 26650's would be most lumens/$? :P
Surely it sounds just like a dream, but I'll try to implement that dream in reality as soon as I get it - it's marked as shipped for two weeks already, but China post has some weird randomness factor with delivery times - that KD driver (as well as six 26650's) arrived few days ago, while being ordered same day as flashlight.