Hi guys i have the same issue of firmware upgrade to 3.01 to 3.03
Reason of the 3.03 admin error is
It's a Tamil nadu firware that we have downloaded so the solution for the router password is
1-password : #@t#w@y or d41d8cd98f00b204e9800998ecf8427e
Try this password instead of blank password for firmware 3.03
2- visit D-Link customer support
If any doubts about the router firmware u can hang me on hangouts
-pradeepvarma107@gmail.com