My problem seems to be solved. My device is DNS320L. I use Windows XP.
This is what I did that worked for me.
Ensure that java is up to date.
First, I flashed the firmware with the latest version which was obtained here: http://tsd.dlink.com.tw/
The file is: DLINK_DNS320L(LW).1.03b04(3.07.0904.2013).zip
Then I ran the setup wizard which was downloaded here: https://www.mydlink.com/support#
The file is here: http://d2okd4tdjucp2n.cloudfront.net/DNS-320L_Setup_Wizard_CA_v1.0.0.0_04242012.zip
Lo and behold, setup was completed and I was able to register my device on mydlink.
After registering the device, I logged out, rebooted the device, logged in again, and device is shown, and files on the hard disk are displayed.