I got kubuntu 12.04 on my laptop, but everytime I try t update, install or something like that it does not recoginze my password, here is what the konsole says...

ernesto@neto-desktop:~$ sudo apt-get update [sudo] password for ernesto: Sorry, try again. [sudo] password for ernesto: Sorry, try again. [sudo] password for ernesto: Sorry, try again. sudo: 3 intentos de contraseña incorrectos ernesto@neto-desktop:~$

and no advance from there, i am some kind of new for this version (12.04 precise pangolin) and i m not sure what is next, thanks in advance for the help and answers!