Welcome To the Fourms!
There are a few things to do. This solved the problem when I had it.
STEP 1: update the firmware. To Do this, go to
http://www.supercard.sc, and select your language. At the bottom of the homepage, you will find a link that says, "DSTWO latest firmware". click the gray link below that. You computer will start its download proccess. Once that has finished, open the folder "eng". Inside that folder is a "dstwoupdate.dat" file. copy it into the root of your sons 8gb sd card. If your computer asks if you want to overwrite the file, push yes.
STEP 2: Update The EOS. Once again, go to
http://www.supercard.sc, only this time, locate "DSTWO latest OS" Click the gray link below it (some people dont, but they should), and it should start downloading. Copy everything into your sons sd card again, and overwrite anything your computer needs to.
STEP 2 1/2 (optional): Add the latest usrcheat.dat file. Just click there -->
http://cheats.gbatemp.net/files/26_03_11_usrchat.dat.zip
STEP 3: Take the Supercard out from the DS/DSi/DSI XL/3DS/3DS Xl. Then take out the SD card. If you have rubbing achool and a Q-tip, take the Q tip and put rubbing achool on it. Clean the contact points on the sd card, then on the dstwo. repeat if nessecary. If you dont have both of these, put the sd card in water (its waterproof if it is micro). WARNING!!! NEVER USE HDROGEN PEROXIDE ON THE CONTACTS!
I Really Hope this helps. good luck!