I am also having the same problem, although the shortcode DOES work withen a text-only widget, but not withen the body of a page. I am using 3.1.3, have tried disabling and even deleting all other plug-ins, have tried switching to the default theme.
I have tried inserting the shortcode using both the visual and HTML versions of the content editor with no luck. I have tried two different plugins with the same results, although wordpress shortcodes such as [caption] seem to work.
