One of the marks of the Catholic Church is that it is apostolic. This means that there has been an unbroken chain of command from Peter to Benedict XVI. The office of the Papacy is unique in this respect.
This unbroken line of succession depends on the power of the Holy Spirit for guidance and that is where papal infallibility comes in. Catholics believe that in matters concerning doctrine, the Pope doesn’t make mistakes. This does not mean that Pope Benedict never wears mismatched socks or never misconjugates a verb in the 42000 languages he speaks in. It means that when a Pope is going to make a huge decision concerning the Church as a whole, the Holy Spirit doesn’t allow him to screw it up. (it is called ex cathedra, meaning from the chair). In this respect ONLY is the Pope infallible.
Catholics do not believe that the pope is perfect. In fact, I am sure he struggles with the same things you and I do. I bet some of those uptight Cardinals drive him crazy at times. He does not stop being human when the white smoke rises. We just believe that since Peter the Holy Spirit has been guiding the decisions regarding His Church.