This is likely that you did not follow the upgrading instructions as stated in the readme.html (but I maybe wrong though).
When updating a plugin, please make sure you DEACTIVATE the plugin first before launching your FTP software to overwrite the files. BUT the best way is to delete that particular plugin folder altogether instead of overwriting it.
When updating WordPress, always DELETE everything EXCEPT your .htaccess, wp-config.php and wp-content folder. After that, then you upload the files in the zip that you have downloaded and run upgrade.php.