In order for the streaming encoders, the video recorder, the video return of MB LIVE to work, it is necessary to set the type of GPU video card in the computer in Configuration \ Webcast \ Other.
1) Auto: auto select GPU (If present). It is therefore usable for Nvidia, AMD and Intel GPUs.
2) NVidia: it is the recommended setting for those who have an NVidia GPU equipped with an h264 encoder, it also allows the use of unlimited simultaneous encoders as explained here: NVIDIA AND THE LIMIT OF SIMULTANEOUS VIDEO ENCODERS
3) None: if you don't have a GPU video card equipped with H264 encoders you can use this option to create the h264 stream using the cpu. Obviously the cpu load will increase a lot and the computer could slow down, but it is the only possible way of functioning until you buy a latest generation video card.
When you change any of these settings you have to restart the video encoders to see the effect.