Publish to PDF - Error "This file is already in use"

I am running a brand new install of X6. How disappointed I was to learn that I'm having the same problem I had in X5 (which I did not previously have in X3, 11, 8, 6 or 4) . . . and that is after I initially publish a file to PDF and then viewing that file as a PDF and closing it, when I go back to my Corel file and make edits and then try to save the PDF again, I get this message: MyFileName.pdf. This file is already in use. Select a new name or close the file in use by another application. The file is NOT open anywhere, nor is it in use by another application. When I complained about this problem while using X5, I was advised by other users to download and install the Unlocker program as it appeared that having published the PDF from DRAW, it was somehow locking the file from further edit, which included re-saving it. I did that, and was able to "unlock" the file so that even though it was NOT open in any other application, it did allow me to save the file again from Draw. Unfortunately, now in X6, the Unlocker isn't even working. It says there is nothing to unlock. And yet I still can't publish to PDF and overwrite the file for some time. Maybe if I come back and try again in an hour or two, it might work. Or the next day it might work. But it will not save and overwrite the existing file if edited within a few minutes of saving and viewing it the previous time. This is driving me nuts, as I often view my PDF's, and then go back to Draw to edit the CDR file, and then publish to PDF again to view the results and make sure all is well with the PDF. Anyone else run into this problem and if so, how have you solved it?