Does your Vizio TV screen go black? Do you still get sound? It could be related to the power saving techniques built in to the TV.
I found this posting after spending some time searching. It took a bit to find the right search query because it is an odd problem.
According to that posting, the backlight power savings control need to be disabled:
1. Bring up the Vizio Menu
2. Select “Picture”
3. Go down to select “More”
4. Select “Advanced”
5. Select “Backlight Control”
6. Change the setting to “off”
The symptom was that during very dark scenes, the screen would go all black (or blank), almost as if it went in to power saving mode. Video would return if the video was stopped to bring up any menu. This setting should resolve that problem, so there is no need for a service call or to return the TV!