SNK vs. CapcomCard Fighters DS has already had its share of negative press; now that it's joined the exclusive club of DS games that don't work, things are just going to get worse. The game-breaking glitch happens when, after completing the game, you start a "New Game +" and attempt to talk to a fellow in the Card Tower named Card Battler John. The game freezes and further progress is hindered.
Depending on your idea of finishing a game, this could make it impossible to play completely through Card Fighters DS. It definitely renders you unable to get all the cards, which, in a game called Card Fighters that contains both the place name "Card Tower" and the name "Card Battler John," is probably pretty important.