next time it is there make a little video of it with your phone or digital camera etc as proof.
Bought an LG 28" HD ready tv in January, a red line has started appearing on left hand side of screen, from top to bottom, its intermittant. Phoned the place I bought it, they want me to phone LG engineer, but because its intermittant Im sort of hesitant, no doubt if an engineer came along it wouldnt be there you know?
Not impressed though, TV is only 4 months old - shouldnt be any problems already.