Aha!!! Looks like we're finally getting somwhere!
Symantec DLO and SEPM are listening on the same port, 8443, so I've changed the DLO port to something else, and will reboot the server to see what happens....sounds like this is the fix to me. I will post an update soon.
This post explains more:
https://www-secure.symantec.com/connect/blogs/sepm-121-and-dlo-75-8443-port-conflict