Solution:

The SD memory card, SDHC memory card, SDXC memory card or Eye-Fi cards have a write-protect tab.
If the <Write Protect Tab> is in the locked position, the following screen appears.

During shooting :

If [Memory card locked] appears in the upper portion of the screen, and [Recordable shots] or [Elapsed Time] shows [0]*, shooting is not possible.
* The above indications may not appear depending on the model of your camera.

During playback :

If you try to delete an image and [Memory card locked] appears in the lower portion of the screen, the image cannot be deleted.

If [Memory card locked] appears on the [LCD Monitor] of the camera, the <Write Protect Tab> of the memory card being used is in the locked (downside) position, so you cannot capture or delete images.
To unlock the tab, slide the <Write Protect Tab> of the memory card upward.