I tried your plugin and it seems to work fine. I easily created a custom style to suit my theme, and it's all good. I'm using WordPress 3.2.1 with the Constructor theme.
I do have a question though: what's the function of the radio buttons next to the tabs, and what does the "Default Start Tab" radio button does?
I know it does not set a tab to be displayed always by default, because when I reload the page, the last selected tab is always selected, not the default one (which I assume is Tab 1)