you may need a firmware update which can be obtained from the dsi store,some games may need diferent codecs or image files to work,out of interest what game is it,if you want to know about flashcarts i will pm you
i did a bit more checking,here is nintendos position on this
Game locks up or freezes
Occasional lockups with video games can happen from time-to-time and do not necessarily indicate a need for repair or replacement. If you are experiencing frequent lockups, or a particular game always locks up in the same area, please see the information below.
Make sure you are using only licensed accessories. Unlicensed products and accessories do not undergo Nintendo's testing and evaluation process. They may not work at all with our game systems, and they may have compatibility problems with certain games or accessories.
Check for visible contamination or foreign material on the connector pins of your Game Cards or Game Paks. If you see contamination or foreign material on a Game Card, please click here for replacement information.
Does the problem occur frequently with multiple games? If so, it may be difficult to determine if the problem is with the system itself, the games, or a combination of both. Please call (800) 255-3700 so that we may assist you further.
If possible, try the Game Card in any other Nintendo DS system (including Nintendo DS and Nintendo DS Lite systems).
If the game still does not work in another system, it is likely a problem with the Game Card. Please review our Nintendo DSi Game Card replacement options to determine how to get your game replaced.
If the game works properly in another system, the problem is with your Nintendo DSi and it will need to be repaired. Please click here for repair options.
If you are not able to try the game in another system, or the above troubleshooting steps haven't narrowed the problem down, it is impossible to determine for certain whether the problem is the Nintendo DSi or the Game Card. Please contact Nintendo's Consumer Service Department at (800) 255-3700 for assistance. http://www.nintendo.com/consumer/systems/dsi/en_na/trouble_game.jsp#lock