Could you - in an emergency - open the last backup you had of the file before you started to get this message?
Then save a copy with a name indicating that it is a copy, e.g. safecopy_current-web-site.rw and take it from there.
You didn’t by any chance change the project’s name, did you? I think RW copes well with spaces. But could it be having trouble with a file name: 'current '?
How exactly did you copy the image; is it possible that doing so may have changed the format?
Is this relevant?