When I got 2 5D3s I bought Sandisk 64GB & 32GB cards and I also bought a Lexar Professional 64GB & 32GB cards. I have noticed that when I put the Sandisks into my laptop the show up instantly on the desktop. When I put the Lexar cards in the SD slot on my laptop they often don't show up the first time or take a minute or two. Anyone else experience this? I am just a little concerned there is something not right about them. They seem to be fine in the camera. Maybe I am overreacting.