Unable to save a file from Photoshop - Windows 10

I pasted an image into Photoshop and edited it to my satisfaction as I've done for many years. But now, when I go to save the image as a file (jpg or pdf), I'm getting the following message "Could not save as "filename" because the file is locked. Use the Properties command in the windows explorer to unlock the file" I tried something as simple as opening a file and changing its name or making one modification to the file and then trying to save it and was denied. In the latter case I checked the security and saw that I as PC user had permission for the file.

But because I'm creating the file in the process of saving, there is no file yet to unlock. How can I get past this problem that I have never seen in 15 years? I recently converted to Windows10 but for a while was still able to save my files. Additionally, I went back to the former Windows 7 that had always worked, I still saw the same issue. So that doesn’t seem to be the problem. I should add that I have a very old version of Photoshop (7.0) which has been more than adequate for my needs up till now.

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