I'm getting an error when opening a file or creating a new file.
Here is the screenshot.
I just installed the 12-2010 version. The 06-2009 version did work for me. I'm running VS2008
You probably have an outdated role path editor extension installed. Try removing the RolePathEditing extension from HKEY_LOCAL_MACHINE\SOFTWARE\Microsoft\VisualStudio\9.0\ORM Solutions\Natural ORM Architect\Extensions and seeing if your file loads.