When you post information about some problem, please include the following details: - OS version (e.g. Windows 2000 Professional SP3); HostMonitor version; problem description.
Looks like old authentication type problem.
Solutions:
1. Try to update libmysql.dll library.
2. Reset MySQL password to pre-4.1 style using SQL query like:
SET PASSWORD FOR 'user'@'host' = OLD_PASSWORD('newpwd');
3. Use ODBC Query test instead of "MySQL server check". You'll need to install MySQL ODBC drivers.