I have problem in slot 1 in Nikon D7100. the memory card was working fine, suddenly it is not accepting the memory card. so when i try to format the memory card, i'm getting the following error message "cannot format memory card. card may be defective insert another card". i have tried with different memory card in slot 1, still i'm getting the same error. so when i try to update the firmware using slot 2, the camera unable to recognize the firmware file. so could please help to resolve this issue.