Somehow the ASUS recovery flash did work, but seems half way, too. The IP is still 10.1.1.1
Now I was able to access the login web page, showing WL500gp.Premium, but I was not able to login with default login/password combination admin/admin or any other combination I can think of -
root/admin
root/root
admin/password
admin/blank
blank/admin
or my dd-wrt login/password combination.