It's pretty common for balls to go off-feed during the winter. If you're
in a climate that gets dry during the winter, that may explain it by itself;
balls come from regions where "winter" means "the dry season", and I think
they base their seasonal cycle primarily on humidity and only secondarily on
temperature. So you might be able to get him feeding by misting his enclosure
regularly for a while.
Failing that, there's a long list of suggestions in Philippe de Vosjoli's
ball python book. If you're not in California, try a gerbil (kill it first!),
gerbils being a primary prey item for wild balls. Try a fuzzy hamster (my
ball pythons have always thought hamsters were some sort of delectable candy).
Leave the snake overnight in a bag with a prekilled food item (put the bag
*in* the vivarium, or you're liable to wake up without a snake). Stand on
your head and beg the snake to eat; it can't hear you, but your friends will
be amused. Repeat all the above. First and foremost, don't worry, and don't
resort to force-feeding until a lot more time has gone by and you've gotten
lots of advice on the subject. In all probability, spring will come (really;
even back east, it will) and the snake will go right back on-feed.
Best of luck,
Qualcomm, Inc., San Diego, CA You should avoid yourself.