It appears that if you install QT after already having a registered copy of DVDFAB on the system everything works fine. The problem occurs with a clean install of QT. In prior versions when I went to register DVDFAB all I had to do was download my registration key, double-click the key, it would self-install and I would be finished. With QT, if I click the key, it will run DVDFAB, but will not register it. To resolve the issue I needed to open the key in notepad, copy it, then open the registration window in QT and paste the key. Once this was done QT was registered and working fine.
I hope this is enough info to help find and fix the problem for future releases. As always, thanks for a great product.