Scroll to the "My USB drive is write-protected". Though this is written around USB, it applies to SD too. http://www.tomshardware.com/forum/
One extra step is to use the SD Association format utility https://www.sdcard.org/downloads/formatter_3/
If none of these work, the card has probably worn out and needs to be replaced.
EDIT: I assumed by "media card" you meant SD card. If you didn't mean SD card, then the last link doesn't apply, but the first link does.