How do we improve loading time of a Shockwave-Director application

My very skilled team has created a virtual reality city and mall in .dcr files.  The graphics for these files has been optimised to the best they possibly can be without taking away from the overall graphical quality of the site.  The objective of the site is to entice shoppers to move around the 3D space, using their arrow keys, and "notice" window-displays as they would in a real life mall/city.

Some of our users are complaining that the application appears to freeze once it is loaded and this is causing a lot of frustration as you an no doubt appreciate.  Recently we loaded the dcr file using iFrame methodologies and in my opinion, the overall speed, once the graphics have loaded appears far superior as opposed to loading into a separate blank window however this opinion is not shared or supported by all users so far.

I am desperate to find a workable and smart solution and am hopeful that there is a shockwave-director guru online who can provide some clues as to how we can overcome the problems.  The site in question is www.popwebcity.com - the city and / or mall can be loaded from the Menu:  Popweb City then Go to City or Go To Mall.  It would appear a majority of the users so far head straight for the mall so this would be a logical place to head to.  

We are looking for a solution on how to make this application load quicker and when it is loaded, is stable so users do not experience "frozen" screens.