We actually had to turn the thermostat off for awhile and then turn it back on. After a few minutes it was working again.
But it happened again this morning. We woke up and were super cold. It was hard to get out of bed. Stephen checked the thermostat and it said 61. Brrr! It's working again now, but our poor furnace just can't keep up with these cold temps. Please, please, please, don't break on us this winter. That would be really bad.