Strange error message...

Hi. When running this script I get the following error “Actor::updateMassFromShapes: Compute mesh inertia tensor failed for one of the actor’s mesh shapes! Please change mesh geometry or supply a tensor manually!”. The weird thing is that this just started recently. I was able to use this code until it suddenly stopped working for a (seemingly) unknown reason. What does this error mean and how can I fix it? Thanks

function Update    (){
	transform.Translate(Vector3.right * Time.deltaTime * 20);
}

function OnTriggerExit (other : Collider) {
	if(other.name=="Right_Wall")
		Destroy(gameObject);
}

Remove the MeshCollider