GRAVITY PROBLEMS -- off topic from {Falsifying a young Universe}

I've heard it many times before but I'd like to see the equations. Is this the comsology arguement, or has someone summed up a gravitational field for a certain mass?The reason I ask is because, you would think that if a certain amount of mass gives off a gravitational field that cancels out it's energy, then an arbitrarily sized mass could appear via hiesenberg's uncertainty priciple.

I can accept that the universe has a net energy of zero, but that doesn't quite address my concern: IF gravity cancels out mass, souldn't we be seeing massive objects appearing all the time (today)because of the Uncertainty Principle?