Try this.
Go to your ZD directory (the "server" side, not the user) and find a file called skin.html in the jetty/webapps/zimbra/skins/_base/base2 directory under that.
Open this file and find a line that reads as following: (it's line #25 in my install)
<!--div id='skin_container_quota' class='skin_container'></div-->
change it to take out the comments so it looks like this:
Code:
<div id='skin_container_quota' class='skin_container'></div>
I saw this in a ZCS install, but I think it could work in ZD.
This workaround may disappear in future versions of ZD and is not likely to survive a software upgrade. Use at your own risk.