I changed the dd-wrt router password and could no longer access the device. Lucky, I was able to login to the router with ssh and default username and my old password. This means that the web gui password was corrupted. With the below steps I was able to gain access to the routers web gui.
- Login to the router via ssh.
- Type in nvram set http_passwd=
- Then type in nvram commit
- open browser, connect to the router and change the password "immediately"
- Power off the router for atleast a minute and power on again.
- login to the router and take backup of your settings.