Can't get picture from my mid '09 13" MBPro to a Vizio TV using a display port to HDMI adaptor
I have MBPro and MacMini with some noname (fitTek) DP to HDMI adapter and it works fine. 

Try to configure resolution to be optimal for External display or to extend it (use as two monitors). 

To be honest I always tried over my Onkyo Receiver- never tried directly into TV