Anyhow, that's not the point. The point is, this month, the gas bill hadn't come in by the 31st, so I didn't pay it when I paid everything else. Instead, I paid it a couple days later... then again, apparently, a couple of days after that, having forgotten that I had done it once already, and it not having showed up on my online banking yet (it takes two days). I put 6 months' worth of future transactions into Quicken, so I can see if there's going to be issues in future months, and so... yea. This system usually works rather well. Whoops. :)
It could be worse; the money is there, and paying a bill twice is better than, oh, forgetting to pay it. And now we're covered for next month. I still feel pretty dumb, though.