Some TVs ask what region you are in after auto tuning, if you are using ITVHD from another region, even though it is coming from your local transmitter, this may be the problem. Once the Olympics have finished, and no doubt another retune is required, try doing it in manual rather than auto mode or possibly select a more generic option from the region list, if available, after auto tuning.
I know of no favourites problems with Granada HD in the Granada area which is why I suspect it is some kind of out of region problem.