It turns out that checkbox is important for S/A to work properly. I remember now I had turned that option off because I have a 3rd party .dll that wasn't signed, so I couldn't check it.
Fortunately, great article here shows how to fix that problem:
Signing an Unsigned Assembly
http://buffered.io/posts/net-fu-signing ... y-signing/
Now, w/ all .dlls signed, I could check the box, sign the assembly, and run S/A, and run the program.