[SOLVED] Error - Black arrow on black screen

[DLX]

Went I go into terminal
Top left:

Ubuntu 14.04.1 LTS T160 tty
Hint Num Lock on
T160 login:

I now remember my full user ID
After typing from other post Sudo visudo

On screen shows must be root to edit visudo.

Don't know how to get to root login.
Have tried
T160 login: Sudo
Pass: xxxxxxxx

Then I get Login incorrect I know this is the right password.

Don't know why this has happened!  Didn't do any update.

Thanks for help