I noticed that Thunar wouldn't open one of my SD cards (it didn't even display an error message when I clicked the shortcut to mmcblk0p1) even though my Windows PC could (i.e. it isn't corrupted), so I checked the media folder and saw that mmcblk0p1 had been renamed to a box with what looked like hex code (like when a browser can't display a character properly) followed by a capital Z and then two diamonds with question marks in them. Can't rename it without being root, it seems, but I don't know if it would be safe to do so with Thunar as root. Would that give the SD card a label? Or would a reflash be the best option?