We consider a dynamic pure exchange economy in which agents have a coarse perception of the future and, in particular, may be unaware of some risks. As awareness of these risks emerges, markets have to re-open to allow the agents to re-optimize and purchase insurance. An ine ciency may nonetheless arise as the cost of insurance is borne at once rather than spread over time. This "savings mistake" is not an issue in two special but important benchmark cases. In those, the ability to re-trade fully negates the ex-ante coarseness of the agents' perceptions. In addition, we discuss the possibility of unexpected default. This arises when agents borrow "too much" and once perceptions change, there is no equilibrium price at which they are able to re nance their debt.