I get the same problem...
I do all the propositions listed above, except copy the slides in a blank new project because it's a quiz activity and a get some error with this kind of manipulation, and nothing work.
I have tried to check and uncheck the Full Screen option, close project, save project and nothing work. I also delete the .dat file.
I use the french version of Captivate, is it possible there is an issue with that version?
I will be please to receave any ideas!!