Pictures and possibly other settings are being mixed when you move from one project to another.
This seems to happen if your Home page has a picture on it.
If you open a project and click the Edit tab, your picture cannot be found because EWB is thinking about the last project you worked on. You can see this in the html as it points to the last project you opened and does not recognize the new project location that you opened. I have made sure to save my projects in completely separate locations.
So because of this, when you open a project and not even make a change, click on another page, EWB prompts you if you want to save the changes.
If you have a picture on your Home page, and you first open up your project, you can see the picture. Then, click the Edit tab and your picture will not be found and is pointing to another project. Then, move to another page and EWB will prompt you if you want to save even though you have not made a changes.
A customer has also found this and is very concerned about pages changing without even knowing it is happening and loses work.