I think files of the main game got corrupted.
If something like this happens again, try to repair the game.
(in Origin > Game Library > right click ME2 > Repair) (in Steam > right click at ME2 > Properties > Local Files > Verify integrity of game cache.)
Thank you for your replay.
How could they got corrupted?
Maybe because I crashed with Shadow before and went back to a save where Liara already left for her apartment. Right after that I started Arrival, never finishing Shadow but kept it somewhat activated in the background.
