I just downloaded and registered MC12, and it appears that I have been charged for the upgrade twice. I received 2 registration codes and when I checked my credit card, there are 2 temporary charges for the 19.98.
I looked for an email address to contact someone directly, but could not find one. If there's something I'm missing, I apologize.
As an aside, I'm updraging from MC10, and am very pleased with the progress seen with the latest version.