It's not a Zen Cart bug. It seems you're missing something.

At its basic level, all Zen Cart needs is for you to edit the configure.php file to match the new foldername.

The error you're getting indicates that you've altered the DB_XXXXXX settings in the configure.php file to point to an empty database, or to a DB_PREFIX that doesn't match the names of the tables IN the database you've specified.