On Fri, 3 Dec 2010 11:22:49 -0800 (PST), Kyle
wrote:

On Dec 2, 11:05Â*am, Kyle wrote:
When the weather here in the mid-Atlantic turned cold in the last
month, we began experiencing a problem in our house we didn't have
last year. [snip]
What I need is advice on what the HVAC people should be looking for
when they come out.

To update on the advice people have suggested:

I think I can pretty much rule out thermostat issues. Got up this
morning - 60.5 degrees when the thermostat is calling for 70, and no
furnace action. I took the covers off the side to see if there was any
obvious issues, and pretty much not knowing what to look for put the
covers back on. As soon as the lower cover tripped the switch (that
prevents the furnace from firing up while the cover is off) the
furnace immediately began its pre-heat cycle (fan to clear the air cap
in the stack, glow of the ignitor, etc.), fired up and brought the
house up to temp.

Weird. I don't know what re-set, but it's been fine all morning and
afternoon (working from home today).

Perhaps the lower cover was loose and vibration was tripping the
switch?? Stranger things have happened.