Just posting this to help anyone else with the same problem that is googling.

I have a win7 htpc in the house running WMC. It has MBAM premium on it.
Out in the sleepout I have an Xbox connected on a wired network, that is used for watching and recording Freeview tv from the htpc via media extender.

Last week the Xbox failed to connect with the htpc.

The solution is to disable the Self Protection Module of Malwarebytes.

(Many thanks to William at Malwarebytes support)