Can you explain further what you are seeing, and where you are getting the workbook from?
I sure can.
When I download the practice workbooks from http://www.tableau.com/learn/live-training-resources I will attempt to open them from Tableau Public and receive the error saying “ The requested workbook does not exist on Tableau Public. Only workbooks that are currently available on Tableau Public may be opened.”
Ohhhhh, you are trying to open them in the Tableau Public desktop application?
I'm not terribly familiar with that aspect - but you could try a demo of the Tableau Desktop application to open them and get an idea.