An older version of Active Administrator needs to be upgraded, or the application needs to be reinstalled.
Installing an Active Administrator agent on a domain controller should not require a reboot.
Removing an older version of the Active Administrator agent from a domain controller should not require a reboot.
NOTE: Installing a newer version of a service can trigger an auto update of server resources such as XML, Java, service packs, etc. Updating any component of the operating system can force an update, including a reboot.