I managed to solve in my Samsung LED TV 40 -
I clicked on the Source button on my TV remote control. Then click on Tools on the HDMI port on which the mac mini is connected.
Then select Edit Name. not type the name, chosen from the list option DVI PC and it was amazing, it worked fine for me, so I have to improve the contrast now.
Seu monitor deve ter as mesmas conficuracoes ja que eh da samsung, boa sorte, tambem sou Brasileiro e passei por esta dificuldade.