I couldn't open the menu and had tab out of the game to close it. Fortunately I was able to fix it a few hours ago. Unfortunately I'm not exactly sure what I did to fix it. Part of the problem was that I forgot what key opened the menu and couldn't find any documentation or game manual. So every time I tried the game again I would just run my hand over the keyboard in frustration. So I don't definitively know if I was hitting the enter key in every test.
Among the things I did was reinstall my video card drivers, uninstalled Camtasia (which has screen capturing functionality that can affect Windows), and uninstalled a bunch of questionable Steam games that could have been poorly implemented. Also I could have not been hitting the enter key the entire time.
So take all that as you will. I love the game. I'll spend $4 for that every day of the week. Please make another.