I have found an extremely annoying problem with the scenario editor in Age of Empires II. When I open a previously saved map in the editor, I sometimes discover that the last minutes or hours of work is gone, even though I am sure I saved the changes before exiting the editor the last time. In other words, it is like I didn't save the last minutes (or hours) of work before quitting the editor the last time.

I am running Windows 7 Home Premium (64 bit). Is this a known problem? If so, is there a solution, or, at least, a way to make sure no data is lost?