Make sure that you avoid these:
*copied from gamefaqs*
*FATAL GLITCH*
If your multiplayer profile name is less than 4 characters long, your game may
freeze and then not be able to turn back on, or you will loose all of your
data. This is called the Fatal Glitch. Avoid it by editing you character
profile and making your name 4 characters or more long.
Also, do not turn the DS off when it is possible the game is still writing to
the card.
Freezing while using the Save and Quit feature is extremely annoying and can be
avoided by not saving and quitting. Instead, put the game in sleep mode to
finish it later, or save the game then shut it off.
If you encounter this glitch, do not restart your DS. Instead, plug it into a
charger and try basically anything you can think of (except restarting) until
the freeze clears.
The fatal glitch was the reason that I didn't get the game when it first came out, but it's real simple to avoid.
