Okay, I am sorry. After some deeper research, it appears maped3 versions around 2005 and EARLIER work, but the 2007 release does not. However, the development version of maped3 (at the time of this writing) on github works.
I have uploaded a build that definitely works on my Windows 7 64-bit machine.
To users that didn't have problems: this new version also adds previewable layer translucency so it's easier to tell how 50% lucent layers will look, and have the editor treat layers as invisible in a form that can be reloaded (the eye toggle only temporarily shuts off the layers, but the translucency settings will persist between edits).
If that works for you, I will make a news post soon.