Originally Posted by Starson17
Did you shut down Calibre completely before the upgrade? By default, Calibre leaves processes running when you close the library interface.
Not that it matters but IIRC, by default, closing the Calibre window shuts down all processes. You have to select enable system tray icon and restart Calibre for the closed window to shrink down and remain running in the system tray.
I have had this selected for so long that the default install setting may have changed since I last did a completely clean install.