as christian has mentioned re: the bent pins ,I can elaborate if you take the ds apart (which will void your warranty so on your own head be it!) take a look at the pins which should be connecting with the cartridge , if any are out of place then you can correct them. Now I haven't got a ds but i do have an Atari lynx and it kept saying "insert game" when the cartridge was inserted ,so i took it apart and using a small flat blade screwdriver (the type you'd use on a watch) i gently bent the pins outward evenly, so they would connect with the cartridge. Put it back together and it worked like a charm. Now im only going on what i did with an atari lynx but im sure the same principle would apply here. Otherwise id consider replacing it. You could always buy a brand new one, swap your broken one for it and take the broken one back to shop and demand your money back. just a thought...
nath
April 2009