Something on your computer, most likely the anti-virus, is blocking the calibre
helper process for file dialogs (calibre-file-dialog.exe). Disable the
antivirus or add an exception for calibre-file-dialog.exe and you should be
fine. Alternatively, you can tell calibre to not use native file dialogs, which
avoids the helper process, by setting the CALIBRE_NO_NATIVE_FILEDIALOGS
environment variable to 1 as described here:
https://manual.calibre-ebook.com/cus...ment-variables