Editor won't load (not In Game Editor)

Hi there, I try to open the Editor from Steam but it appears just a black screen and it doesn't load at all. I see from my Task Manager that, while the Editor is loading, it suck up 17% of the CPU so I have to quit the process because the Editor won't load even after some minutes. Any help? The game and the editor are both located in the Data disk of my laptop.

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