I managed to solve the problem by tweaking my nVidia settings. Here's what I did, in case someone else has a similar problem.
- Go to the nVidia Control Panel and set Advanced Settings.
- Under "3D Settings", click "Adjust image settings with preview"
- Click "Use the advanced 3D image settings" and then click "Take me there"
- Click the Program Settings tab
- Click "Add" and find your thLabyrinth.exe file
- Make sure it's selected in the dropdown and apply custom settings. These worked for me:

(Off, 8x, On, Override, 4x, Off, 3, Multiple, Off, Clamp, Quality, Off, Auto, Off, Use 3D application)
And voila:

Curiously, it fixed the text issue, too. I'm not knowledgeable enough on what I just did to know why, but if it works, it works.