Moniter(hdtv) goes black when playing games

I have my computer hooked up to a Magnavox 42" HDTV through a DVI-HDMI cord. When im playing World Of Warcraft it will occasionally go black for about 5 seconds than come back on, and my computer stays on. It seems to do it in areas that have bright colors. It used to do it before i installed new hardware. I now have a Nvidia 8800 GTs, and used to do it when i had a 7800 GT. I've tried adjusting the refresh rate and other settings but nothing has worked. Please help me, because it will screw me over when in raid or arena. My comp info is as follows...


AMD Athlon 64 x2 Dual Core 5600+
4 GB Ram (Crucial high performance DDR2 PC2-6400)
Seagate SATA/300 500GB/Go
Asus M2N-SLI Deluxe
Windows Vista Pro
Current temp- 86 degrees Farenheit

 

How about the model of the Magnavox TV?

There is no "Vista Pro". There are 4 different Vistas: Vista Home Basic, Vista Home Premium, Vista Business, and Vista Ultimate.