I posted this fix as a reply to another thread, but thought it might warrant its own since it seems to be such a common problem.
So, as you all know, the firing button frequently refuses to work, causing no end of frustration and sore thumbs. Why this occurs is a mystery (to me, at least), but I think it may have to do with dust or debris left over from the manufacturing process. Anyway, here's what you can do:
1. Get a can of electrical contact cleaner (WD-40 might work, but no guarantees).
2. Attach the plastic tube to the nozzle (make sure you buy a brand that comes with one. I lost mine, but a very thin coffee stirrer works too).
3. Remove the bottom cap from your LT, place the plastic tube right up against the switch innards and blast a couple of times.
4. Shake out any excess, punch the firing button a few times and it should be good as new. Was with mine.