When Velocity is started or stopped, it writes to the Windows Event Viewer under the Application logs. If the Application log are full, and not allowing Velocity to write to them, this message box will occur.
To fix this issue, use the following steps:
Open Computer Management through your system’s search bar
Under System Tools, expand Event Viewer, expand Windows Logs, right click on Application, select Properties, then enable Overwrite events as needed
Making this change will allow Windows to write events to the log, and depending on the log size it will overwrite events as needed and prevent the “NT Event Log is full” event from being generated.