Ubuntu :: Changing Username - Password Not Working On Restart

I did these steps to change my username: I like to directly edit /etc/passwd and /etc/groups

First open a terminal, become root
Code:
sudo -i
Now:
Code:
usermod -d /home/new -m old
sed -i -e 's_old_new_g' /etc/passwd
sed -i -e 's_old_new_g' /etc/group<-
sed -i -e 's_old_new_g' /etc/shadow

My computer shut down after I did the second step and now my password isn't working! I cannot open my home folder or get back to root!