The crash occurs, as you thought correctly, when I am trying to update different fields in the window schedule. There is a certain format that our firm uses for schedules, and the window rough openings listed on the schedule aren't directly linked to the windows in the model. I've had this happened a couple times in the past, and sometimes deleting the schedule and making a new one takes care of the problem. However, as you can imagine, that solution is really annoying and timely.