By default when a pc / server connects to an SUS server, an susclientid is created on the pc / server. In case that you clone that pc / server, the same susclientid will exist on the cloned pc / server and the SUS server will only have one entry of this pc / server. In order to change it on the new pc / server you have to follow the following procedure:
1. Stop Automatic Updates service
2. run regedit and go to HLM/Software/Microsoft/Windows/CurrentVersion/WindowsUpdate
3. on the right site of Registry Editor delete SusClientId and SusclientidValidation
4. Start Automatic Updates service
5. open cmd and run: wuauclt /detectnow
Now a new susclientid will be created on the machine and in a few seconds it will be created on the SUS machine.
Tested on Windows XP SP3 for the moment.