Problem Loading Site Map Generator

Hi
I can’t seem to load the sitemap generator in my browser (using Vista, I.E.7).
When I load the screen from the browser, I get the orange Java Box & see the white loading bar giong up. When the loading screen goes, instead of loading the generator, I just get the grey background. I’m using the latest java version & have tried the memory workaround (-Xmx256m).

Thanks in advance for any help!