Bike stalling on cold mornings

Hey everyone, I've been having some problems with riding my bike (2000 Virago 250cc) in the cold mornings (6:30am). It stalls whenever I stop and gets real sluggish when I slow down and try to speed up again. It has been serviced by a Yamaha Professional about 2-3 weeks ago. I have been told that the temperature shouldn't affect my bike, but when I ride it home from work in the afternoon when it's warmer, it doesn't skip a beat.
What's going on?