Thx all, looked for it but I didn't find it as that one seems to deal with xbox, though I got 2 thoughts. I tried some of them, 2 worked out and now it's running:
1.- Run as administrator: I already had that selected, but I made sure to launch it with right click, 'run as admnistrator'.
2.- At the same time, I didn't ALT + TAB and waited until the characters' selection screen.
Doing both things, the game is running again. Now I'll try to find out which (or both) are needed.
Thanks all for your help !