After upgrading the AutomationEngine and Initialdata components to 10.0.4, the ability to start an agent from the System Overview and/or the modify_system command. There is no error message associated with this, the commands and actions just do not work.
This is due to a incompatibility between older Service Packs and Hotfixes of the Service Manager and the 10.0.4 AE/DB components.
This has only been able to be reproduced on Windows.
Upgrading the Service Manager to 10.0.4 should resolve this issue so that starting the agents from the System Overview and the modify_system command will work.