I am in Canberra - Dont ask why, but I have 4 TVs in my house running off 3 different antennas. My main TV a LG Plasma and a no name LCD TV run off the best antenna. A cheap Kogan LCD runs of a low set antenna and an old CRT TV runs through a HD STB off an old antenna that has had most of its rods broken off.
Recently, my LG Plasma started showing that Channel 64 (64ME) was an invalid service - thinking that it was a TV programming issue I rescanned all channels and it shows Prime Channels 64, 65 and 68 are an invalid service. On checking the no name LCD on the same antenna I find the same but there is audio. The Kogan TV on its own antenna is the same sound but no visuals on the same channels.
So I think that Prime has done something to their signals - HOWEVER on checking the CRT TV with the STB and the crappy antenna, it has a full service on these channels with vision and audio - full reception.