Are you using a new card or just changing sounds on the card that came in the caller?
Things to check for:
You may have a script error in the program. Try reinstalling the foxpro software.
If you are using a built in card reader make sure it is not set to read only.
There have been issues reported with built in card readers in HP laptops being incompatible with Sandisk SD cards. If you are using a built in card reader on a laptop you might try a different card reader.
Your SD card must be formatted FAT32 for use with the Spitfire.