I've had similar problems as others here in making a slideshow. What I did:
I opened all the images from a specific folder into Fireworks
I created a new document
I selected "open content" in Commands>make a slideshow
the folder shows up, when I click the folder in the top list the files list in the bottom
I go to "export path" and choose the folder, and over-write the folder
I click create and the system goes through the "motions" of creating the slideshow
Now I back out ... and reopen the slideshow creator ... seek to edit the existing slideshow and am told the file "slideshow.xml" does not exist. I've done this several times and had the same result. it acts as if the slideshow is being created when all I get is the subfolder for thumbnails and nothing more.