The bug relates to players saving in Lumiose City, the game's capital and largest city. Players affected by the bug are said to be unable to load their save files, with no apparant solution other than deleting and starting over.
Nintendo is yet to acknowledge the existence of the bug.
Both American and European versions of the game are said to be affected, alongside physical and digital copies of the game.
Pokemon X and Pokemon Y launched last week, and have sold over four million copies worldwide since launch.
For more information, check out GameSpot's review of the game.