Error in admin when using plugin

Hi,

We’re getting the following errors/warnings when using your plugin:

Warning: mysql_query(): Access denied for user ”@’localhost’ (using password: NO) in /home/eur123/public_html/wp-content/plugins/database-and-memory-usage-limits/database-memory-limit.php on line 187

Warning: mysql_query(): A link to the server could not be established in /home/eur123/public_html/wp-content/plugins/database-and-memory-usage-limits/database-memory-limit.php on line 187

Warning: mysql_fetch_array() expects parameter 1 to be resource, boolean given in /home/eur123/public_html/wp-content/plugins/database-and-memory-usage-limits/database-memory-limit.php on line 190