OK, so that eliminates that ... I've thrown a 2TB in mine, so thought that might be the issue.

I have a few splitters etc running signals around the house ... my last resort is that the signal is too low on the frequency that the TVNZ transmitter is on (there are three transmitters, the other two are ok mediaworks/kordia), However looking at the signal strength meters etc it looks ok/the same and a TV plugged into same place has no issue... work in progress