I know this is an old post, but the problem is with the crappy French SCART system (hate it!). The TV is receiving a signal from SCART 1, the Sky box (usually just when the adverts appear!!!), which it thinks is telling it to switch to the SCART 1 input. Only solution, switch off (preferably) or switch to stand-by, the Sky box - it won't happen then.
Swapping the SCART leads round won't help, my configuration is the other way round, DVD - SCART 1, Sky box - SCART 2, and it still happens if the Sky box is on...
SussexRokx, July 2011
