What's wrong with the Summa Theologica?

I've heard that there were two points of Catholic doctrine in Aquinas' Summa Theologica that were later successfully defended to the contrary. One, I think is the Immaculate Conception of Mary (although I don't know where that is in the Summa) and I'm not sure what the other one is. Excluding things that might not exactly measure up to modern science. What are the points of doctrine in the Summa that don't line up with Eternal Law?