That is very strange. When you say that no image shows up, do you mean that it's a white image or is it still the blue "please wait" image?
If you don't want the thumbnails to open the next time, you can right-click the tab header and choose "close" and answer the dialog box that you don't want it to automaticaly start with vncscan.
Best Regards,
Samuel E. Crane
Senior Support Specialist
support@vncscan.com