I'm here because my new SD card (SanDisk 32GB) stopped working. It has been in my phone for a couple of days, and I moved all possible apps and music to it. It was fine for another day but when I turned it on this morning, all of those apps were greyed out tiles.
I rebooted a few times, then I pulled and reinserted the card a couple of times. No help.
I put it in my PC card reader and saw a long list of corrupted files. Just garbage characters in place of file names, dates, and sizes. It may have had something to do with adding some extra music yesterday or not, but now it looks like I'll have to wipe it and hard reset and see how far the restore gets me.
Wish me luck!