This problem usually only occurs under the following circumstances:
You are launching an application with a user interface from EventSentry (e.g. notepad) - not a command-line application.
The EventSentry service is configured to run under a user account other than the LocalSystem account (e.g. a domain user).
You should be able to resolve this problem by re-configuring the service to run under the LocalSystem account, however please note that it is not recommended to launch applications that are visible on the desktop. Applications launched from EventSentry have, by default, elevated privileges and a misuse of the application poses a security risk if an intruder were to take control of the application.