I've recently purchased a new GXR with M-mount from SRS here in the UK. I have tried both 'standard' Sandisk Class 10 64GB and Sandisk Extreme Pro 95MB/s 64GB SD card. However, when I tried to format them for the first time, it shows 'card error' for both cards. I have not set up anything on the camera. And both cards are brand new. I have tried both cards on my other cameras. They both work fine. What should I do? Are those two cards just not compatible with GXR? Which 64GB SD does? Help, please. Thank you in advance.