I am rehabbing an old house. I am working on the first floor right now and have not begun work on the second yet. On the second floor over the last week I have noticed paint bubbling off the trim around my windows and doors, and the wall underneath one of the windows. It is happening in more than one room. I have owned the house for 9 months now, and have done no painting in thses rooms yet. I know there are a few causes for this, but would it take this long to begin bubbling? The areas were not freshly painted when I bought the house, so it has probably been longer than that. Any help would be greatly appreciated. Thanks in advance.