After going back and reviewing….I can only think of two things.
1.) Some kind of driver issue between the HD Homerun and the Ceton (doubtful: I have this combination, as do many others, but I don’t use the HTPC for live TV too often but I haven’t seen what you are describing).
2.) Are you using a separate NIC for the HD Homerun? If so, what type? What you could be seeing is that while the HD Homerun is in place the HD Homerun is creating additional interrupts which is causing an additional load on the system.
