Got my miniDP to HDMI adapter today and hooked it to my TV. Despite of overscan issues, I'm having an issue when I switch off my TV or change the input. The iMac still thinks the external monitor is connected even though I have switched it off and thus my desktop is extended. Does anyone know how to fix it? Any utilities that let you enter "single display mode"? The TV is 32" HD ready Sony and I've used the above mentioned miniDP to HDMI adapter.