Opening a PDF in calibre changes the default "Open with" app
Windows 8, 64-bit Calibre
Downloaded a PDF
Used the Windows explorer to locate the file
Right-clicked and selected "Open with..." calibre.exe
Calibre added the file to the library
Then clicked on the PDF linkon the right-hand side of the screen that usually opens the item for viewing.
Instead of opening a viewer, it added the PDF to Calibre again, and again
And, attempting to view any other PDF stored in Calibre added it again.
Went to windows Explorer examing the properties of the PDF
Observed that the default "Open With" app had been changed from Acrobat to Calibre.
Changed the Default app back to Acrobat
Went back to Calibre, clicked PDF and the book opened in Acrobat
This problem does not occur on the Mac and I think it is new on Windows, as I have done this procedure many times before and never experienced this behavior until now (1.10).