Cannot transfer files to and from SD card

[SouthBerm]

i have a micro SD card with an adapter that used to work fine, but now says that the disk is write protected, so therefore I can not add any files to the card. Any advice?

[Calum]

Check the card for a small toggle switch.
Try it with the switch one way, then try it the other way.
You've probably accidentally caught the switch (easily done) and made it write-protected.
Hope this helps.