I have had this problem with my sky hd box. I am now on my 4th box in 18 months. When it works every thing is great. The samsung box seems to give a better picture than the old thompson box. Complain to sky, they should change the box if still in warranty. If you are out of warranty threaten to leave sky unless they fix the problem, they will replace the box free of charge. Don't take a maintenance contract as these are simply not worth it. Hope this helps.
Cyrus CD6SE, Cyrus 8VS2, Spendor A5.
Kimber Crystal CU, Kimber 8VS, RA Power Kords.
Sony BDP S550, Pana TXP50S10B, Marantz NR1501, Sky HD.
Kef 2005.3, Kimber PBJ, QED cables
QED interconnects and cables, 2X Tacima CS929.