So I just purchased a brand new Toshiba Satellite A665-S5183X and It works great with my new smaller bedroom LCD TV via HDMI and automatically connects when I plug in the HDMI.
HOWEVER, my older 42" Plasma connected via HDMI will not recognize each other. The TV says it isnt receiving signal and the laptop isnt showing a 2ndary display in the graphics settings. The HDMI cord works and I watch COX via HDMI to the older plasma TV.
If you have connected the notebook to an external monitor press FN+F5 key combination to switch between monitors. Also make sure the cable is connected before you turn on both monitors. Then turn on the TV and select the correct HDMI input channel, now turn on the notebook.