Two USB drives with Media Server?

I finally got around to plugging in two USB hard drives to my RT-N56U today. They were both mounted/recognized on the GUI, but when I tried to share them both on the Media Server, it only allowed me to choose one drive - and only one folder on that drive. Is this a result of the newest firmware (I loaded 318 today as well) or has this been a limitation all along?
Thanks.