Fatal error with wp 3.5.1 and plugin version 0.63

Installed the plugin, went to the plugin page under Tools, got the following error:

Fatal error: Call to a member function query() on a non-object in <site directory>/wp-content/plugins/wp2epub/wp2epub.class.php on line 225

http://ww.wp.xz.cn/extend/plugins/wp2epub/