When I run the game at native monitor resolution 3840x2160, the game no longer accepts mouse clicks. I can move the mouse around and everything, but clicks aren't accepted.

Same here, cant play the game since my monitor don't accept lower resolutions and game dont run in windowed mode...

I had wondered where the game would break. I had no problem at 2560x1600, but I guess 4K kills it.

Though it might be possible to run at a lower resolution and have your graphics card scale it, even if your monitor only supports 4K, though that seems strange in of itself. You can't play blu rays because they are only 1920x1080?

Are any other selections available in resolution NWN. Try the config tool.

What GPU do you have? You should be able to set it to have the GPU scale lower resolutions.

1080 gtx.
Of course downscaling works, but that's not the point :)

I mainly answering the post right after yours, that said his monitor would not accept lower resolutions. Usually that can be gotten around.

I think now is working, thanks