Did your mmc got corrupted?
you can try to repair it.
All the memory cards are based on the FAT file system and not on the FAT32 or NTFS
file system. for repairing you will need a corrupted mmc, a mmc reader, and a PC,
obviously.
1) Insert your memory card in the mmc reader.
2) Find the drive in which it is inserted from your pc.
3) Now, in the file system selection part, select the file system to be FAT and not
FAT 32 or NTFS file system.
4) Right click the selected drive and select FORMAT but NOT quick format.
5) Start formatting.
Its Working