Capture complains design is opened read only when it is not

Hello everybody,

For some weird reason, OrCAD Capture complains that the design file is opened read only, even when it is not.

If I right-click the .dsn file in explorer, and click properties, the read-only checkbox is not checked.  I can rename, copy and delete the file no problem (I have a backup).  If I delete the opj file, and open the .dsn, at first, things are fine - I can edit and save.  I then close the application, and the .opj file appears.  When I open the .opj file, OrCAD capture complains that the file is read only.  What the heck is going on?

Is there some obscure option I have selected by mistake?  Has anyone had this happen before?

Any help appreciated.

Cheers,

Allan