CTP4 Project System -- Not Backward Compatible
CTP3 Project files can not be opened in on CTP4. If you are moving from CTP3 to CTP4 you will have to create new project files. If you have work that you want to capture a current state of a project you will have to deploy that state to a server and then RE it into a new project. When we made the change in project system to split the file and schema views this changed the project system file layout.
