I don't think this is a SWISS-specific problem. So far, I've had temperature problems on pretty much all my transatlantic flights, be it in Y or C, be it on (then) Swissair, BA, AA......
Especially on night flights, it seems like they turn up the heat in order to make it easier for people to sleep. But I just start to sweat and sleep is gone....
Never had a problem on European flights though.