Lightroom not working on Macbook Pro (2014)

I've just bought a new Macbook Pro, 2.8 Ghz i7, and I've installed Lightroom 5.6 via the Creative Cloud. Everytime I open the software, after the splash screen, all I've got is a grey window (where the actual software should be displayed). Also, I've noticed the top menu is reduced to only "File, Edit, Window and Help".

I've tried uninstalling and installing a few times, and the problem persists.

Here's what happens:

I've also tried downloading Lightroom 4, that actually works (but since my previous laptop already had the Lightroom 5, I've lost a lot of presets, so, I don't consider a downgrade an option).

Any clue on how to work around this problem?

Thanks