OMG. You guys are life savers.
My heater stopped working with EXACT same symptoms. The temp is supposed to get down to near freezing tonight and my heater wasn't working.
I read this thread 3 times and studied the manual before going up in the attic to investigate my Lenox 80UHG unit.
After unplugging the hole of the inducer, I now have heat and my family can sleep without being cold.