It's funny, there was just a RadioLab show on NPR on this subject
. They talk about another guy who had a different type of brain damage (tumor removal) which seemed to leave him normal at first, but made him horribly indecisive. They figured out that his emotional response center was damaged. Without the emotional push to make a decision, he would never feel pressure or other emotional drive to make the decision, and couldn't do it. The emotional part is apparently just as important as the logical part in making a decision.