[Plugin: Google XML Sitemaps] Your sitemap is being refreshed at the moment.

I recently moved all my sites from one server to another and now each of them displays this “Your sitemap is being refreshed at the moment. Depending on your blog size this might take some time!” at the top of the xml-sitemap page.

It’s now not refreshing when I add additional content because I guess it thinks it’s already being built. A manual rebuild works but I still get the same message.

I’ve tried to deactivate and re-activate but that’s not working, any ideas?