Make sure you don't have large zip files or perhaps zip files with a lot of files in them on your desktop.  The browser tries to parse that data (not us, the control we're using)
We have found that putting them elsewhere avoids the issue.
 
Keith

I mis-spoke in an earlier post. 
 
I was thinking that the slowdown started when I used different screensets, but it was actually Mix Recall that started slowing things down.  On my test project a have several Mix Recall scenes.  Is there any way to speed up the loading and saving of project files that have more than one Mix Recall scene?