I'm using a SanDisk MicroSD Ultra 32GB in my Galaxy Tab2 10.1. I put the first one into the tab when I purchased it new last month. The card seemed to work fine for a while and then after a few days it refused to accept new writes. I can still read the files I've copied to it but I can't add or delete anything. It's like the card is in read-only mode. I tried taking the card out and formatting it on my desktop PC but Windows reports it's unable to format or delete any files due to an unknown error. I figured I got unlucky and bought a bad card. So I purchased another one this week and put it into the Tab. This time the card seems to be working because I can still format it however if I try to copy anything to the card on my Tablet I get an I/O File Error. Does anybody know what might be wrong? I'm running the standard Samsung ROM on my tablet - 4.0.4. Thanks for the help!