The DSi rolled out a new firmware v1.4.2 at the beginning of May 2011.  Till now, the following cards are compatible with 1.4.2 once they have been installed the corresponding firmware 1.4.2 fix:

1.    R4i Gold 3DS Card (r4ids.cn)
Please download and install the latest driver “Wood_R4iGold_V1.29b” and firmware “R4iDS_Gold_V1.4.2b_Patch”.
The driver and the complete setup guide are available from the R4i Gold 3DS setup guide:

2.    SuperCard DSTWO
Please download and install the latest driver “DSTWO v1.11_0512”.
The driver and the complete setup guide are available from the Supercard DSTWO setup guide:

3.    R4i SDHC v1.4.1
Please download and install the latest driver “v1.38b”.
Note: for those failed to upgrade the R4i from v1.4.1 to v1.4.2, please run the latest firmware fix [name of firmware fix programme] to upgrade the R4i v1.4.1 on the NDS Lite console. Afterwards, please download and unzip the kernel v1.38b to the microSD card to be used with the R4i v1.4.1.
The driver and the complete setup guide are available from the R4i SDHC 1.4.1 setup guide:

4.    DSiplayer
Please download and install the latest driver “iPlayer OS & firmware – 1.4.2”.
The driver and the complete setup guide are available from the DSi Player setup guide:

Meanwhile, the following cards are expected to be compatible with DSi v1.4.2 once the manufacturers have released the firmware fix in the very near future:
1.    R4i SDHC 3DS
2.    Acekard 2i
3.    Supercard DSONEi Mini
4.    Supercard DSONEi
5.    iEDGE
6.    EZ Flash Vi

Please stay tuned for further updates. We will be sending out newsletters once there are further updates.

Besides, if you are not sure about the firmware version of your DSi, here's the guide on how to check firmware:

1. Click SETTING (with the Tool Icon) on the main menu

2. Check the right hand corner of the top screen which says VER 1.x

VER 1.x is the version number.