Update-notifier sending false alarm?

I’m using the latest version of WordPress (3.0.1), and have had the Update-Notifier plugin installed for some time. For some reason, I recently started getting emails with the following:

It’s time to update the version of WordPress running at https://site-here from version 3.0.1 to 3.0.1.

So, I downloaded a fresh copy of the plugin, and found that it’s the same as what I have enabled in the plugins directory. I traced the above message in the email to the following lines of code in update-notifier.php:

$update_core = get_site_transient( 'update_core' );        if ( ! empty($update_core) && isset($update_core->updates) && is_array($update_core->updates)
                && isset($update_core->updates[0]->response) && 'upgrade' == $update_core->updates[0]->response
        ) {
                $newversion = $update_core->updates[0]->current;
                $oldversion = $update_core->version_checked;
                $blogurl = esc_url( home_url() );                $message = "It's time to update the version of WordPress running at $blogurl from version $oldversion to $newversion";

It seems that the following two variables:
$update_core->updates[0]->current;
$update_core->version_checked;

are the same, yet $update_core->updates[0]->response says to upgrade. Is there something I’m missing, or is this a bug?