The HDMI specification supports what are called CEC protocols this is essentially a language to allow to devices connected by HDMI to talk to each other and allow autoswitching and a whole host of other functions. THE SKY HD BOX does not use any of these functions so do not expect autoswitching or any other functions when using it. Indeed Sky apparently contrary to the HDMI spec have pin13 (the one used for CEC communication) connected to earth when if unused it should be open circuit, this has apparently caused situations where attaching a SkyHD to a group of succesfully communicating devices has stoped all CEC functions working focrcing some people to insulate the pin or cut the connecting wire to stop the other devices being confused by the incorrect connection to earth in the Sky HD.
There are some exceptions, Panasonic primarily who implemented an additional system in their hardware that will autoswitch to a HDMI input based simply on the TV's internal circuitry detecting the HDMI input going active/inactive. Incidentaly the reason Samsung SkyHD boxes do not autoswitch even with Panasonic is apparently they did something very odd in the hardware that leaves the HDMI in a permanently active state even when the box itself is in standby so even the Panasonic system can't work because the connection never goes from off to on.
