Thanks for your help! While this method does work, what I ended up doing is making an alias out of the Unix Executable icon which I then put in my Applications folder right beside the official Calibre icon. I still don't know why it won't open normally, only through the Terminal. I opened Console.app to see if any error messages came up but there were none. Very strange. If there are any Mac experts out there who can help, I would be greatly appreciate it! Thanks!
