I also noticed those SD cards used with Ricoh GRD IV and GR are protected. Photos can only be deleted in camera not PC but still can transfer photos to PC and from PC transfer firmware files into the card.
Maybe you can ask for replacement from sandisk since other SD card are working fine with GR?
Yes, I'll check with SanDisk, but my concern is there are photos inside the SD card and I can't remove them before asking for replacement. Lucky this doesn't happen while I'm on vacation, the card has been with me on many cameras (Canon 60D, E-P3, NEX-7) but never had any issues.