Yesterday I upgraded to WordPress Stats 1.8.5 on my WP 2.9.1
When I want to call /wp-admin/plugins.php I get the text
Future upgrades to WordPress.com Stats will only be available in Jetpack. Jetpack connects your blog to the WordPress.com cloud, enabling awesome features.
and nothing else.
When I look into the HTML source, I see
<b>Fatal error</b>: Call to undefined function is_multisite() in <b>/www/htdocs/...../wp-content/plugins/stats/stats.php</b> on line <b>26</b>
I have to manually rename the FTP folder and thus disable the stats plugin to get access to my plugins page again.