When i try to transfere the nds file to my r4, they say i cannot and that is is write protected. Any one can help me with this pls?
I assume you are running your card through an SD card adapter. Turn off the lock switch on the side of the adapter and it should work fine.
If there is not a lock switch on your adapter, then your MicroSD is likely corrupted/becoming corrupted. Backup any files you can, and try to format your MicroSD using an SD formatting program. http://www.sdcard.org/consumers/formatter/