Hey guys, been having a problem with my late 2011 13" MacBook Pro recently.
When I received this at christmas (and when playing about with it before christmas) I used the thunderbolt to HDMI adapter for HDMI output with my tv and it worked fine, no problems at all. One night a couple of weeks ago I was outputting to my TV with it fine, turned it off then the next day I tried to plug it in at my girlfriends house and it would not work. The screen goes blue on the MacBook like it normally would, so it is recognising the TV, or at least recognising that an HDMI cable has been added. But yet it still does not show up on the TV. I have since tried it on my TV many times and it still does the same. I have even bought a new adapter and HDMI cable and it still didn't work fresh out of the packet.
I'm running OSX Mountain Lion 10.8.2 (12C60).
The adapter I'm using is pretty much identical to this one: