[Plugin: DB Cache Reloaded] Not work at 3.1

error said:

DB Cache Reloaded Error: wpdb class is redefined, plugin cannot work!
Previous definition is at /home/yusuf81/public_html/sjnetcab.com/wp-includes/wp-db.php:52.

DB Cache Reloaded Error: DB Module (wpdb class) is not loaded. Please open the Options Page, disable caching (remember to save options) and enable it again. If this will not help, please check FAQ how to do manual upgrade