LG 42LF66 LCD TV. 42" FULL HD picture quality

Hi all.
Just purchased and took delivery of my LG 42LF66 42" LCD full HD 1080P.
in HD mode i am very very impressed with the quality through my Sky HD box. But when watching none hd sky channels like bbc1 and 2 etc the sharpness goes and it seems like the colours are smudging. does anyone have any advice on setting the picture settings and quality up on the normal channels as i think i have got the HD channels showing in excellent quality. I had a Phillips 32" LCD 768p before and never had this problem. Please post me any advice.
many thanks in advance