I put this NEW sd card in my NEW GS4 for the first time, and now the metal contacts are scratched and it randomly unmounts from the phone!  My older 32GB SanDisk works just fine, so I'm thinking its the thicker paint or something causing this...  I don't know, but its ruined!  It scratched the first day, but I'm just now noticing the unmounts now that I have my music on it, every few songs it will unmount and remount, interupting my music...  I'll never buy another expensive SanDisk.  I'm going to order a different brand, just make sure I can find one without paint on it....  Sucks, I really thought this was going to be a good one!  I love the colors, and its so fast to transfer files to.... too bad its broken.  And I didn't find out about it until after the return date, so i'm screwed.  Oh well.  Never again, I'll give my business to someone else....