Kurinji,
Could this be similar to the conversation discussed at
http://millenia.cars.aps.anl.gov/pipermail/ifeffit/2014-August/012075.html ?
It does appear quite possible to "break" an Artemis project file in such a way that it cannot be re-opened by Artemis. This can happen if one does a fit and then re-runs Feff. I don't know enough about the layout of the project files to know why this happens.
But, it would be most helpful if you gave more details (like, what operating system and Artemis version your using) and included a project file that showed the problem.
--Matt