I have not 100% exactly the same, but a very similar issue.

I use the Steam engine, and it works just fine when I launch the classic DOS2 Editor, but when I attempt to launch the one for the DefEd, it straight up won't load. The loading window doesn't even show up, although steam shows me briefly "playing The Divinity Engine 2" before going back to not in a game.

It worked just fine yesterday when I was working on my mod, but the update today appears to have broken something.


Hope I can help solve the above issue and mine by also providing some of my specs:
Windows 7 (x64)
Alienware
INTEL i7-48000MQ
16 GB RAM
NVIDIA GeForce GTX 770M