I love this particular song because it's more upbeat than the vast majority of their music (but with more of an edge than "Littlest Birds," of Weeds soundtrack fame). "It's Not Happening" compliments a cold day like an Irish coffee: warm and soothing, but with a bracing kick.
Full disclosure: I usually get a general impression from a song before examining the lyrical meaning. It was only after about the third listen that I realized "It's Not Happening" is more complex and ambiguous than it seemed at first...give a listen and decide: is this happy or wrist-slitting music disguised as a plucky Canadian folk tune?
On iTunes: The Be Good Tanyas / "It's Not Happening"