I'm running version 2.56 with a Macbook version 10.10.5. When I try to open Calibre, I get the bouncing icon, then it disappears without loading the app. I created a new user in OS X and was able to access my libraries. This happened several installations ago & I've just been switching users but this is less than optimal. I've seen several suggestions in the forums. I'm not sure whether to completely uninstall (and if so, how?) or delete prefs (couldn't find that file?)
Thank you for your suggestions!