You do realise that having purchased the program you have the right of direct support from the developers. That's the main advantage of purchasing the commercial versions of Piriform software.
Choose the program from the "Select product" drop down menu and get their help directly ...
By the way, if I knew why that was happening (which I don't) I would help as would the other guys on here, but maybe better to take advantage of the direct developer support.
It's ran successfully by thousands upon thousands of users without an issue like this so I don't think it's a simple problem with Recuva.
Have a try at running it in "Safe Mode" is all I can think of, and if that works it suggests there's a conflict of some kind with something else on your computer.