Could just be the battery gets low and the cold pretty much kills it.
But is it normal for the button to lose the click? I have noticed this twice.
Today really sucked because I was out in the cold and the dark. The light was on. I shut it down for ten minutes and then it would not turn back on. The soft click that I usually feel when hitting the button was gone. It is a good thing I had some PB Superflashes and a Blackburn blinkie or else I might have gotten run over by a plow.
It was 6 degrees F (-14 C).
I do not know anything about this stuff, so I might be missing something obvious.