American Standard Freedoom 80 furnace starts to run, then stops?

I have a 2 year old freedom 80 furnace. never had a problem until today. It starts to run for about 30 seconds. I hear burner start to ignite then shut off. LED is flashing on-off continuously at about the rate your cursor flashes on your computer, the manual says this is normal "cal for heat". Any help would be greatly appreciated. Cold in Woodstock!!!