I logged in and everything looks as it should and I also tested some other widgets in the Showcase area. But you are right, it just doesn’t want to load up in the page. I also loaded up Widgetkit on my local test site but I cannot replicate the issue you are experiencing with a missing slideshow. I also disabled all plugins to see if there might be a conflict somewhere. However, it appears there is a problem with your install of Widgetkit, which seems to be related to your instance only. This is actually the first I’ve heard of this happening so something is unique about your setup.
Although I do not provide support for third party plugins, the only thing I can suggest at this time is to totally remove Widgetkit, then try a reinstall with a new slideshow being created and see how this second attempt goes for you.