There are quite a few exercises that can strengthen your lower back, but to echo Torlyn, if you are getting a "pop" in your back that temporarily paralyzes you (

), you should IMMEDIATELY CEASE further training until you talk to an MD, I don't want to rag on you, but you should have done that the first time that happened. It doesn't take much to completely screw up your back for the rest of you life.
I have to concur...your back will make or break your life/lifestyle...they can give you some fancy limbs that work well but I have yet to see a new back or anyone return to full functioning after serious back injuries and/or surgeries...
HL