Funny i had the same problem with a watson 28" widescreen tele.....i took it back and upgraded to a 32" which doesn't have the same problem but i was told by the maufacturers that it was a problem with the sky box....Sky said problem was with the tele...so the upshot is don't know how to help other thsn to tell you it is an issue Sky should be aware of and as you say the diffs is only on the Sky channel i would see if it happens with another decoder if you can borrow one.