Cannot render 16:9 video for youtube
Have you tried to disable graphic card rendering? Incompatible graphic cards or drivers may cause the exact symptoms you describe. Preview may not use graphic card rendering, as this is controlled by another setting.


Select Options|Preferences 
Go to tab card "Video" 
Set "GPU acceleration of video processing" to "Off"
When rendering: Open your render template and select Encode Mode:
Render using CPU only.