Having an issue where multiple drives (External HD's via USB and an SD card inserted directly) will no longer mount when plugged in. If I open Disk Utility I can see the drive listed but the volume it contains is greyed out since it is not mounted. I can then click on the volume and mount it with Disk Utility. It then shows up in Finder, etc. and is completely usable. I have no idea why I suddenly have to do this, disks and the SD card slot always mounted just fine before.