A couple of people have reported similar symptoms when levelling (
Video Crashing on Level Up -- NPC issue w/Fix), but not just opening the skill list, that I recall.
For the Steam version, did you try verifying local files? In the Steam library, right click on Divinity Original Sin and select Properties, switch to the Local Files tab and then click on the 'Verify Integrity of Game Cache...' button.
Please email supportdos@larian.com, with a description of the problem and the report.zip file generated by the
D:OS support tool (for the PC version). The report will contain system and game information, any crash dumps, and your saved games (which are probably not directly relevant, so all but one can be deleted from the zip to reduce file size).