If you've been playing Pokémon X and Y, hopefully you haven't encountered the Lumiose City save bug. And if you did, hopefully you didn't start over.
For those who thankfully missed out on this particular issue, a number of players were reporting that saving in the game's "hub" town of Lumiose City was corrupting their save files, making the game unplayable without restarting. The issue would arise if you saved your game in the "outer ring" of Lumiose City, as well as in the southern side streets that led into the center of the city.
Nintendo promised a fix, and they've delivered. A 229-block download (which you'll need to grab twice if you own both Pokémon X and Y) fixes not only the Lumiose City save bug -- including restoring corrupted saves to working condition if you haven't overwritten them already -- but also an issue with the Global Trade System that would sometimes result in a communication error when attempting to search using filters.
This being Nintendo doing something Internet-related, the update process is a little more cumbersome than it perhaps needs to be -- you'll need to open the eShop on your 3DS device, accept the update and then tap several "download" buttons in order to set the process in motion, but once it's all done with you should have a fresh and fully-working version of Pokémon X and/or Y to play with, and you can get on with your journey through the new game's Pokémon-infested take on France.