i feel your pain.
I have stopped squatting for that reason. Even with 135 on the bar, my back goes.......i just can't take the pain and frustration anymore. Funnily enough, deadlifts are fine.....they don't give me a problem.
But i have stopped squatting......i'd like to lift for as long as i can, so as much as it pains me, i have reluctantly thrown the squats on the scrap heap......it's just not worth it anymore.