It was on being "dead to the law", ie, that the Old Testament legalism couldn't save, and why, and what that means for us - we're working on Galatians, have been in the second half of chapter 2 for about a month. He packs a lot into 45 minutes, though.
Sounds good! Galatians is a book I really get a lot out of. When my friend was taking a class on it in grad school he taught a course on it at our church, and we spent about a week on each chapter; it was one of my favorite classes.