MBP to TV under higher performance connection problem

Hello there.
I have no image when I connect my MBP to my LG TV under higher performance.

More details.
I have a MBP 15" with Snow leopard 10.6.8
I connect an adaptor from mini display to HDMI in the mdp
Then an HDMI cable to the HDMI input of my TV.
I get no image to my TV but I have image in my MBP when I use higher performance (NVIDIA GeForce 9600M GT).

However when I use better battery life (NVIDIA GeForce 9400M) I have image in my TV and also in MBP.

I tried to find new drivers for NVIDIA GeForce 9600M GT from the oficial web site of NVIDIA and I get a massage that says that they do not support my device any more.

thank in advance for any help.
Anduan

I fixed it finally ! ! ! I just reinstall the snow leopard and everything works perfect.

I just installed the update 10.6.8 for snow leopard and it did it again. I have no image at my TV under higher performance. Something is going on with this update . . .

I also tried to see if I could solve this problem upgrading to Yosemite but the same problem still exists. And I can not understand.
My Lg TV screen works perfect under higher performance only with Snow Leopard 10.6.3