The Ur-Yuuzhan Vong was the term given to the proto-historic members of the Yuuzhan Vong race.
The name was given to the race from which the modern Yuuzhan Vong evolved from and were the early beings that were completely connected to the Force. These early Yuuzhan Vong lived in symbiosis with one another and the species as a whole.
However, when the ur-Yuuzhan Vong became too proud of their individual accomplishments, they were suddenly cut off from the Force, after which they turned to violence. Modern Yuuzhan Vong religion attributed this to their deities namely Yun-Yuuzhan and that he had sacrificed his body to create the Yuuzhan Vong people. Thus it was the gods and not the Force that created the Yuuzhan Vong.
The race were cut off from the Force because of their desire to escalate themselves. But in time their religion became so twisted that they believed that the only way to return to their gods was by escalating themselves. This resulted in their devotion to pain, sacrifice and death, which drove them further away from any reconnection with the Force.