My door gets more cantankerous when the weather turns cold as well. Every year I have to lube the hinges and rollers, and tighten all screws and bolts. Then I lube the chain and the cable roller.
Then I run it up and down manually to see if there's a bind. If so, I do whatever I must to fix that. Occasionally, a roller will break off it's stem.
Try all those things. Then, if necessary, adjust the "down" power adjustment on the unit.
[This message has been edited by rpxlpx (edited November 19, 2002).]