i bought 4GB SD card for my camera and it was working as it should be. i could take photo's then transfer them to my pc then delete them from the SD card. I could transfer the pics from the SD card either via the camera and usb lead or by the usb card reader i have. i then bought a digital photo frame and put in my SD card. it worked fine and happily scrolled through the pictures i had on it from my camera that i hadnt deleted yet. so i deleted all the photos from the card and put it into my digital photo frame and now i was watching photo's that i want. But........... i now cannot add anymore pics to it or delete any as it says it is write protected. also when i put it in my camera for the extra memory i cannot take any photo's as it says protected card! how could i have done this and how can i undo it? TIA