I found a work around in case someone else has this issue. I borrowed my wife's laptop and installed Divinity: OS. The interface for leveling up stats works fine on the laptop, so I can update the save game on her laptop and then copy it back to my desktop.
My video card doesn't seem to render the level up interface correctly, so that the "plus" buttons don't work. The laptop has an AMD Radeon HD 7660G card, and my desktop has an Nvidia Geforce GTX 650 card.
