Okay. No asplosions...
They fixed it. Well, actually, I called my contractor and he sent someone to fix it. So I know it's done right.
Anyone ever watch "Holmes on Homes"? I've got a contractor kinda like that. I feel like the cavalry just arrived when his truck pulls up!
So - it's fixed. Scary though - it was just inspected in July! My contractor says it's probably because of the extra pressure put on an old system by installing the furnace. That it might have found weak spots that would've been fine otherwise, but since there's more gas going through now, the weak spots couldn't take it. Or something like that.
All I know is that I'm really really glad they found it and that's it's fixed!