I am sorry to hear of your problem .I have the MS250 and a MS250C which is the pull the starter rope a couple of times and it spins the motor for you. Today was cutting wood with a larger saw for several hours and was concerned about the slack. Tightened it up and cut for 5 more minutes and put the saw in the back of the truck for a half hour ride home. Never thought about it cooling down in the 15 degree weather, If you can still pull the chain around the bar with a gloved hand I would think things would be okay. I would try to find someone who knows what caused it.