Something on your computer is interfering with the calibre worker process calibre-file-dialog.exe which is used to display the open file dialog. Most likely your antivirus/security program, or a program that install windows shell extensions. Either you will have to find and disable the program or you can use the
CALIBRE_NO_NATIVE_FILEDIALOGS environment variable as described here:
https://manual.calibre-ebook.com/cus...ment-variables