What room are you carbing them in? If it worked when you were using your furnace and now isn't working when you're using your AC it might just be a temp issue in the room you're using and they are carbing, just doing so more slowly.
Thanks Gameface, another good suggestion. But typically my cellar where I store them is a very consistent 68 degrees throughout the year. I have a feeling that the additional mixing of the sugar & wort in the bottling bucket did the trick.