It's more that he's infallible when discussing certain things, under certain conditions:
"The Pope is preserved from even the possibility of error when he solemnly declares or promulgates to the universal Church a dogmatic teaching on faith or morals as being contained in divine revelation, or at least being intimately connected to divine revelation. It is also taught that the Holy Spirit works in the body of the Church, as sensus fidelium, to ensure that dogmatic teachings proclaimed to be infallible will be received by all Catholics."
no subject
"The Pope is preserved from even the possibility of error when he solemnly declares or promulgates to the universal Church a dogmatic teaching on faith or morals as being contained in divine revelation, or at least being intimately connected to divine revelation. It is also taught that the Holy Spirit works in the body of the Church, as sensus fidelium, to ensure that dogmatic teachings proclaimed to be infallible will be received by all Catholics."
http://en.wikipedia.org/wiki/Papal_infallibility