My brother has just returned two Sony LCDs with very strange faults. There was a screen-burn type effect where the BBC news channel logo from an HDMI input was faintly showing whilst viewing from its tuner- even after the HDMI input was removed and the TV turned off and on again later.
Also there was a strange audible tone due to incompatibilty with a Humax box (that has not been an issue on any previous TV)
Richer Sounds confirmed the faults and refunded. He bought a different model Sony TV from John Lewis (as Richer didn't stock it)- different model, obviously common parts as exactly the same problem. Back to John Lewis, swapped for a Panasonic. No problems with that.
Don't think you're alone gel. With new models more frequent and competition fierce, you have to wonder whether corners may be being cut, hopefully not in QC departments.
I know of two people who've had the lines down the screen problems with LG sets, but then every brand has someone with a horror story.
I've never strayed from buying exclusively Sony and Panasonic myself. Although, don't LG supply the panels for other brands these days?
Hope your problem gets sorted to your satisfaction.