Check out the video to the right (or here) to see an unsual way to overcome a sticking point in your squat: the ISO-DYNAMIC Squat. Set up the pins at your trouble spot and do several sets of 3-6 repetitions with :02-:06 holds. Be sure to attempt to fully exhaust yourself driving into the pins.
I'm in the middle of 5x2 back squat right now. - Sarah