Installed a Honeywell Rth7500 today. Heat worked fine for about 4 hours. Now the system only blows cool air even though the thermostat shows heat on. My wiring is as follows:
c, b, g, y, r, and w2 plus extra piece of 18 gauge wire connecting it to E (the old thermostat had w2 and e sharing one wire)

It is possible the beater broke or is having other problems unless the wiring you did today came loose or is failing to make proper contact. I would revisit the work you did earlier.

Thanks for the quick reply, I'll follow your suggestion and see what happens