There is a limit on the number of files and folders in the root directory of a FAT16 filesystem of 512.
This number is reduced much further if file names longer than 8 characters are used.
When transferring the files onto the card, it is very likely that new files will be rejected after a certain number by your memory card reader.
A workaround is to either keep your filenames under 8 characters in length or keep your files in separate folders, so they are not all in the root folder.
