When you run IPSentry as an NT system service, you must be sure that the user account under which IPSentry is running has rights to various network components being monitored. We recommend that IPSentry be run under the exact same account that is used to configure IPSentry to avoid security configuration variations that might interfere with proper monitoring. 

For example, if you configure IPSentry as Administrator but run it under a standard user account, the security context will be incorrect and you may begin getting security access errors, credential errors, and etc.