Hello, has anybody had a similar problem and maybe can give some advice here?

I recently bought a new SVR-HDT500 from Bluewater Sony Centre - I have been very happy with it for a couple of months, but now I have a very annoying issue, during play-back of recorded TV (HD and normal channels) picture is jittery or jumpy, although the sound track seems to playback OK. It appears as if frames are missing, and video appears to be jumping forward several frames quite frequently....