problem of "source /etc/bash_completion" in gutsy

[aries]

cat ~/.bashrc
#######################
if [ -f /etc/bash_completion ] ; then
    . /etc/bash_completion
fi


alias pp='ls'
#######################


if i source bash_completion , then i notice that all the contents below 
" . bash_completion" will not work.

When i commented it out , the "alias pp='ls'" will work again.