This reply is only half a year late - but since this is the first hit on Google, perhaps it will help others.
If you have a DVG-1120m and can't reach the Advanced screen because you don't know, or have forgotten, your password, this should enable you to work around this and flash the 1120m to an 1120s - and in the process, reset your password.
First off, kudos to sigmaz over at FWD for an excellent post that got me most of the way there. His thread is:
FWD User Forums :: View topic - D-link DVG-1120M/S for FWD IT WORKS!
Download this file:
index
Unzip it.
Unplug your connection to the internet, plug in your DVG-1120m in this order: Router -> DVG-1120m (WAN) and then DVG-1120 (ethernet) -> PC.
You should get a new IP from your DVG-1120m that looks like 192.168.15.X - where X is a number. Next check that you can reach the web site for the 1120m by typing:
http://192.168.15.1. It should be there... if not, then the rest of these instructions will be no help. Also, the rest of these instructions assume windows, but linux/mac should work too, but you'll need a different TFTP server and the command path will be different, but the idea will work.
From Windows, open up a command prompt (Start -> Run -> type "cmd").
In this black window, type "telnet 192.168.15.1". At the username prompt, type "admin" and at the password prompt type "admin" as well. Yes, these will work even if your web password for the advanced menu is something else. Or at least it worked for me.
You should see:
192.168.15.1 >
If not, then I'm not sure what went wrong.
But assuming you can see this, you now have access to the console of the DVG-1120m. You can smile and be happy.
Once you are finished being happy and want to proceed, you can get a list of commands by typing "nwdbg". If you want to see the current configuration, you can you type "nwdbg config".
But as cool as all this is, it doesn't help update the firmware to an 1120s.
Go to the directory where you unzip the files above and run the file "dlinktftpserver.exe". Note the IP address in the upper-right corner.
Next at the nwdbg prompt type, "tftp" to get a list of tftp commands.
Type these in sequence:
tftp srvip <tftp server IP noted in the upper-right of the TFTP server>
tftp get 1120S_runtime_s08.tfp
tftp update
and then wait while the device clicks and lights blink. When the prompt comes back to life, type:
tftp get 1120S_promcode_b09.bin
tftp update
then
nwdbg system reboot
Now the IP address of the newly flashed DVG-1120S is 192.168.0.1.
Re-telnet back in again, log in with admin/admin and type:
nwdbg factory reset
And that's it. You should now have an 1120m... if all the above instructions worked.
If they do work for you, please post back with your experience.