I'm having the same problem as marsch_z and bossehund. I have no other plugin installed, and tried different themes, right now with boilerplate just to make it easy to html5. It doesn't work anyway, it creates the space but doesn't animate.
I don't think it's something about other plugins or themes, because I tried to run the example in the "How to work with HTML5 Swiffy Insert" page and it worked correctly. It may be some incompatibility between the google swiffy generated code and the plugin.