This warning message on the AZ252 is usually because the SD or SDHC memory card is full. Use another SD or SDHC memory card (after formatting it) or delete unnecessary files after saving on your computer or another device.
This warning message could also be because the SD memory card in your AZ252 is locked. Remove the SD card and slide the lock switch to the 'UNLOCK' position. Reinsert the SD card and try to take a test photo.