I've been breaking in my new B44 outside in the cold.. between 10 and 25 degrees, and it has a problem of cutting out very frequently.

I am running a Havoc 8.5 with a 21 tooth pinion/84 tooth spur, 2s lipo, Futaba 3pm 2.4ghz radio, w/ deans plugs.

My brother's xxx-4, which uses the same esc/motor and a similar battery, had the same problem a while ago, but it seems to have gone away now.

Can lipo batteries stop functioning properly at cold temperatures?

Yes they loose capacity when cold. Which also means they loose the ability to handle the high amp draw as well. You really shouldn't be running them that cold, you risk damaging the pack.

Jason