Could this be a similar experience?: When a jet travels faster than sound (which occurs every day in air travel), an observer hears the sound in the sky in a slightly different location, opposed to where the jet is seen in the sky. But, the auditory signel does not change the jets actually physical location.

When working on my computer, upstairs, I notice a slight time difference between the sound on the downstairs cable HD TV, and the upstairs cable non-HD TV (when they are both tuned to the same station). Anyone know why? I suspect HD signal takes a slight time longer to process in the HD TV box. I have also noticed that on HD,sometimes when peoiple speak, it seems the sound is slightly off the visuals (it seems like people talking are doing a poor job of lip synchronization).