Known causes:

1. ClayCentray was not run as a service. I.e. ClayCentral was run directly from the Start Menu or install folder instead of running the ClayCentral service (Control Panel/Administration Tools/Services/).
   
   
2. On some machines, all interactive applications are closed when the user logs off Windows. Solution: In Services, open the ClayCentral service Properties, click on the 'Log On' tab, and uncheck “Allow service to interact with the desktop”.