House not staying warm at night

I have a 10 year old furnace and thermostat (sears programmable digital thermostat). Recently, on some nights, the furnace doesn't seem to be kicking on enough, and we wake up to the house being 10 degrees colder than it should be. We'll have the thermostat set at 73, and the house will be 63... and the furnace won't be on...
Usually, at some point in the morning, it kicks on. Or, sometimes i go downstairs and power off the entire furnace (there's a switch by the furnace) for one minute, then turn it back on, and it's starts warming the house.
At first I was concerned that the programmable features of the thermostat was screwing up, so I set it on a constant temperature. But that didn't seem to make a difference. It doesn't do this every night... but more nights than not now.
It's cold here at night (single digits farenheit), but it's not an unprecedented cold. The furnace has never had this problem before.
My questions: * Should I start with assuming the thermostat is bad? I can replace that myself (I'm comfortable with following wiring schematics, etc...) and that would be cheaper than a service call.
* Has anyone experienced this kind of problem before?
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On 10 Feb 2007 06:31:13 -0800, snipped-for-privacy@gmail.com wrote:

Yes, Replace your thermostat. Its almost always the thermostat. Then, if that doesnt work, you will need to install a bigger furnace. Change out the low voltage wiring too so it will acclimate itself and match the impedance of the thermostat circuitry. You might want to try a few duct boosters too. Bubba
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Why don't you guys suggest Man to by anew house that is lot easer, really unbelievable.
wrote:

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Another stupid reply by bubbs!
Let's hear a cheer bubba!
HAHA
-Canadian Heat
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Another stupid reply by DANgER,, all he can do is attack other posts but he's incapable of answering the question
I guess he likes to be heard.
WE HEAR YOU!!! TOO BAD YOU HAD NOTHING MORE TO SAY THAN THE OTHER POSTS!
CAN YOU HEAR ME NOW? IF YOU WANT TO OUTSPEAK ME INCREASE YOUR CAPS SIZE
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Sounds like the system is locking out, meaning there is a problem with the furnace. What kind of furnace is it? It could have a 3 hour lockout and then try to restart. Sounds like a simple maintenance would be the best bet. Check for an LED light or something flashing a code down at the furnace.
-Canadian Heat
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On 10 Feb 2007 20:51:10 GMT, DANgER ( snipped-for-privacy@heat.com) wrote:

Locking out? Hey, good guess Canuck. Who'd a thought? Bubba
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