I have done all that you said Julian. But nothing is working. I mean for all the actions or commands I'm doing it just gives the error
TNS-01169: The listener has not recognized the password. I'm confused.

One more thing you told me to remove the Listener entry. Does it mean that I should delete the entry for my current listener in th listener.ora file and kill the listener and retype the entry for it in the listener.ora file and start it fresh. OR Delete the listener.ora file completely and create new file?

If I kill the listener and restart will it restart successfully? OR will it ask for password again for restarting also?