Wikipedia offers a list of cardinals who were excommunicated.  You're right -- history suggests that there have been many instances of conflicts between cardinals and the pope, usually not the pope who made them cardinal, but a successor.  Cardinals (especially in the curia) opposing the pope, or attempting to control or undermine him, is nothing new or particularly shocking. However, the incident with the Knights involves a situation in which Burke not only disagreed with the pope (Burke is entitled to his opinion), but misrepresented the pope in a situation where it was Burke's job to represent faithfully the pope's wishes -- whether or not he agreed with the pope. If the pope decides to impose some sort of discipline on Burke, it will not be due to Burke's disagreement but to his malfeasance.