Those problems are often related to the Audio stream in the recording, rather than the video stream.
9HD and 7HD use a Dolby AC-3 audio stream, while most other channels do not. For example, ABC and SBS HD do not use AC-3. However, 10HD does use Dolby AC-3, so have you checked recordings and Live TV on 10HD?
Check the channel properties in the "Options > Television > Channels > Manage Channels.
If 10HD also exhibits the problem, then look to fixing the audio playback. I don't know exactly what the answer will be there, but Buffers are often an issue. There have been threads on AC-3 playback in the past, so a search may find an answer.
PS: I'm in Melbourne and have no issues with any channel on MC25.0.115 64bit.