Excluding mhddfs completely since I'm not using it, I see similar results in MythTV in what I assume are high bit rate portions that could easily be resolved with a bit of buffering.

I have all my TV on a NAS connected via HomePlug powerline so it's not the speediest in the world - maybe 2-3MByte/sec average.

The untuned signal at the beginning of HBO shows reliably stutters (probably doesn't help it's right at the start though). Certainly sections where bitrate should go up cause problems.