I'm running WP 3.1.1 and WP-E-Commerce 3.8.2. I have the latest versions of both Google XML Sitemap and your plugin.
Here's the sitemap:
When I don't have the plugin installed, Google's Sitemap generator seems to work fine. Once I activate it and rebuild the site map it adds duplicates of pages - but I don't see any products in there.
Any idea whats up?