I tried most of the sites mentioned above and did have much success.
So I tried this alternate site and it seems to work fine:
I was able to download a map image for Georgia that I think will cover the region for an upcoming 300k brevet.
It works differently though in that I could only get it to create an image file to download directly to my GPS.
The original site created a Windows executable that would first install maps in MapSouce, which then was used to download a subset of the maps to my GPS.
So now I am still missing the piece where I can load maps into MapSource.