I am having this problem since installing 14.04.

Here's the line I entered into my fstab:
UUID=xxx-xxx-xxx-xxx  /media/wd4tb ext4 defaults 0 0
Naturally, the xxx in the example are the real numbers of the drive.

When I boot, the drive shows up on the left hand side, but dropbox and my copy app can't see it until I open it in Nautilus.

Any ideas why?