The plugin is referenced here - http://wordpress.org/extend/plugins/hover/. When activated several WP functions are not available. These include (but may not be limited to) the "Screen Options" and "Help" links "drop down" but have no content. Also, when creating a post, the "Discussion" options do not display.
Now, it is NOT completely broken. If deactivated when posting, etc, all the issues appear to go away. Then, upon reactivation, the functions that the plugin does (at least the ones I use) appear to work as advertised.
So, if you can work around the above issues, and want the hover functions... ;=)