I have the same issue (ver 5.1.0.342) on any project that I try to open. I can create a project and create DVD’s as long as it’s all done in the same session but as soon as Encore is closed the project can no longer be used. Since I have to render everything rather than using Dynamic Link I am going to switch to using the Corel VideoStudio for generating DVD’s. It’s not as powerful as Encore but it always works and is ok for my needs for now. Hopefully Adobe will address this issue soon since it seems to have been an issue in version 4.0 as well.