I performed an uninstall and reinstall of the ThorUI AU from scratch and I can't seem to replicate the issue you are having.
Can you be more descriptive with the step you are at when you recieve the error or is it immediately when you click on the "Window Wizard" button?
Thanks in advance,
FYI
I'd also recommend posting in the
ThorUI AU Help [Need Help with the Auto Updater? Post here!!!] forum as Robert/MrNice monitors that thread for issues related to his AU program as he may be able to assist you better than I could.