OK so you're working on two versions of the same project, two different project files saved in the same project folder, both accessing the same media, you close the current one and open your latest backup, and when you try to save that backup again you get the message - correct? Were you trying to save that backup under a different name?
thanks for your time
I'm working on multiple cues/files for the same film score. They are separate cues (10 mins each) using the same source video file and one or two small audio files. Each cue is a separate project file saved in the same project folder. I may have at one point had two project files open at the same time.