Apparently it wasn't that bad of a loss if the Green Bay Packers only slipped down to No. 7, while the Bears moved up to No. 5. From the NFL Power Rankings:
The Packers didn't play their game on Monday night against the Bears. They're still an elite team in the NFL and will be hanging around the top 10 all year.
The thing I found puzzling this week was that despite the Falcons beating the Saints, in New Orleans, the Saints are still at No. 3 while the Falcons are down at No. 10. I'd reverse those rankings based on what I've seen so far. The Saints haven't looked very impressive this season. They've only outscored their opponents by 5 points overall, and a last second victory against the 49ers is not looking like an impressive feat.