I am always happy to help out former students. I have looked over the ingredients you sent me, a straightforward Draught of Peace if I'm not mistaken. It is in fact, quite a difficult potion to brew correctly and if not done so, can lead to the side-effect you mentioned. A well-practiced potioneer would have no problems with it, but it is generally not for amateurs.

Are you quite sure the potion in question was brewed sufficiently? If you are, I will revisit your original inquiry, but I would normally chalk this one up to an error in the brewing process.