A fellow developer has the same error issue when he tried to open a site he built. Not sure what his versions of Web Designer Premium are.

This is an issue. Magix/Xara support acknowledged the issue and the solution was to open the file and remove the smart shapes. Which of course is a challenge if you can't open the file to be able to remove the offending objects.

We have over 100 Xara sites and if smart shapes are going to start prohibiting us from opening sites to update we have a real problem.