I saw this effect on a demo with a recorded Sky HD football match in my local John Lewis store.
You could also see it on the Sky Sports HD logo (DOG) when it was panned quickly over the crowd.
On speaking to the salesman we disovered that deep within the setup menus for the set you could turn the vreal processing down or off which gets rid of the problem at the slight cost of losing some fine detail in the picture on fast movement.
As with most picture processing engines you pays your money and takes your choice... as they say.