Lucy, you've got some 'splainin to do.
Why are we seeing this on an N900? Actually the answer is easy. The Ovi Store website checks the "user-agent" string on the web browser that is accessing it. I changed the user agent string in the Maemo browser to mimic an Android 2 Google Phone, so I can use Google Buzz. The Ovi store thought I was a Nexus One, so it told me "Go away, we're closed".