I created a slideshow 620px x 250px in a page on site created with the Responsive theme. It looks fine in Google Chrome, has an issue in Firefox ... and fails to display at all in Android 2.3. There's nothing at all on the page at the point where the slideshow should be positioned.
I'll look into this later. I don't have any mobile debug tools, but I'm sure there'll be a way of determining why it's not shown.