DS LITE Then it would seem like a problem in the ds lite itself, possibly the game card reader is faulty. Service required. I'm sorry about s4u311 have a look over here http://www.nintendo.com/consumer/repair/dslite_repair_home.jsp

Your DS cartridge reader is faulty. Unless you know how to take the DS apart and replace the reader by soldering, you should just buy a new one.

I'm sorry to say this, but if by 'card reader' you mean Game Card Slot, then your system is modified, and in the process of doing so, the person 'fixing' it damaged it worse. It is now no longer fixable by Nintendo, and the system is will continue to be a black hole of money for you if you continue trying to fix it.

I recommend cutting your losses now and buying a new system.

Possible that the new downloads have errors or unrecognised files which are detected and so will not be processed. Yes there is not much to be done than to clean , remove and reset. Also the older set cannot be faulty as it plays all the regular games and so you need to recheck once again for the compatibility of the older set with the newer games or if these are supported ones.
Please take consensus before even the set is removed as the fault seems relative to data processing.

reinstall the DS drivers from comp.

You can play multiplayer games with a Nintendo DS Lite even if you don’t possess a copy of the game. If one of your friends has a multiplayer game card, they can use their Nintendo DS Lite as a host for the game session and you can join the multiplayer game.
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Things You'll Need:

• Nintendo DS Lite

Using One Card to Host the Game
1. Step 1 Look on the game’s packaging for the "Multiplayer" icon. If the game requires only one player to have a copy of the game, the icon will show two DS Lites: a DS Lite with a black screen transmitting waves to a DS Lite with a white screen. Below the two DS Lites is a range of numbers which indicates how many players the game can support.
   
2. Step 2 Put the game card in the Nintendo DS Lite that is acting as the host for the multiplayer game session and start it up.
   
3. Step 3 Have the other players turn on their systems. They will use the main menu screen to access the "DS Download Play" icon. They need to tap the icon to begin downloading the game information from the host DS Lite.
   
4. Step 4 Begin playing when all of the systems have finished downloading the game information from the host.
   
Multiple Cards for Multiple Players
5. Step 1 Look at the "Multiplayer" icon. If every player in the game session needs a copy of the game in order to play, the icon will show two DS Lites, both with black screens, transmitting waves toward each other. A range of numbers is under this graphic and indicates how many people can play at one time.
   
6. Step 2 Read the game's instruction manual on how to set up the game session. The steps required vary by company and sometimes by title within the same company.
   

*reposted from ehow.com

Hi,

Not that common a problem. Have one on my desk at the moment with the same problem. It seems that the game bent two of the contacts in the card reader (ds lite game section -slot 1). I opened the slot and straightened the two pins and this solved the problem.

Be careful if you are doing this as it is quiet tricky with a good few small parts.

ur game reader inside of ur DS is dirty or faulty. First try blowing air into it, is that doesnt solve it, im afraid youu'll have to take it to nintendo, they'll fix it up for a fee.

Yes you can buy it in the ebay...

Regards,
VOTIT

Why don't you buy a R4 or Acekard, something that can go into the Slot-1 of the DS?

there is an error with the ds itself, you will have to get it sent off for repairs or find a nearby gaming repair shop