Dear John, Tso and all reading this post, I could able to fix the problem successfully with the script uploaded by John. The problem with the getpass that I could fix with the help of the script I got from here:
http://talk.maemo.org/showpost.php?p=405435&postcount=5

Now the mytube is downloading and playing youtube videos successfully...well, for the first time in my N810 use. Thanks guys for taking me to the promised land:-)