Hello All! Hopefully someone will be able to help me out

I'm using a Mac Pro OSX 10.8.5. I've just installed the latest addition of Calibre. Yet when I double click the icon, it just bounces on the dock and then quits. I did some searching and found out that when apps do this, the trick is to right click on the app, go into "Show Package Contents", then "Contents", then "MacOS", then double click on "Calibre" (which is a Unix Executable File). This opens up Terminal which in turn opens up the app from there. The app runs fine after that. However when I quit out and try to get back in by double clicking the icon like normal, it just bounces on the dock and quits out again. So it seems like the only way to open up Calibre is through the "Show Package Contents" method. This is obviously a hassle! There appears to be something on my system blocking the opening of this app the normal way and I'm just wondering if there is a way of determining what it is, or if there is some simple Terminal command which can help to clear up this issue. Thanks so much for your help in advance!