Hi, I have a rMBP since mid 2012 and never needed to use the SD Card reader. Today I found my old SD Card adapters along with some cards. When I inserted the card, nothing happened.. tried 2 different adapters with 2 different cards. Nothing. When I rebooted the rMBP with the SD card inserted, there it was. This happened twice with both SDs. If I eject and reinsert the card, nothing happens again.. until I reboot that is. Any fix for this? Is my hardware defective?