Sounds fairly obvious to me...too much lube in the firing pin channel, combined with being left out in the car in extremely cold temps. Excess lube will do strange things to firearms in the cold. My father's Browing shotguns always misfed while hunting in cold temps, when there was excess oil on them (he didn't know any better).
In World War II, the Germans resorted to using no lube at all in their fighter plane machine guns while on the Eastern front. I read this was the only way they could get them to work consistently in the extreme cold temps.
"...the men under your command deserve your leadership."-OXCOPS