Acekard not working in one DS but works ok in other DS

Hi,I have an Acekard which works fine in 3 out of the 4 DS lites we have in the house. On the fourth DS it worked fine until a short while back when it suddenly stopped working. On this particular DS we have also recently found it wont play some other games which used to play OK, but still plays others fine. The DS just shows the 'DS card not inserted' message when the Acekard is put in.
Any one have any ideas??

Your DS may have dirty or bad contacts on the Slot 1 (NDS Slot). It might not be making good contact. You could try to gently blow it clean, or take a look in the slot to see if anything looks dirty or bent.