This an encoding compatibility problem that occurs when there is a discrepancy between wordpress encoding configuration and the default system or server configuration.
The plugin creates tables like so:
$sql = "CREATE TABLE $this->dbtable (
.... Code ....
reviewer_name varchar(150) DEFAULT NULL,
.... More table fields Code ..
)";
The DEFAULT keyword is the culprit here since this is using the system / server default encoding and not the wordpress one .
An Easy way to fix this is to log into phpmyadmin and manually change the encoding from latin (or whatever is your default) to utf8_general_ci