Have i bought wrong hdtv?

bought full hd lcd tv while watching sport in high def in full screen it goes blurry still picture ok the salesman said it would be ok it was 60Hz.why is it i get cyrstal clear pictures while watching sport in picture in picture little screen even in standard def channels.tv is 1080p hitachi 42".what can ido can i take it back to jb seeing though he recommened it to me over similar samsung units.did he recommend it to me because hitachi are leaving aust in feb u think?