I nearly had to give up running a few years back because of a degenerated lower spine (prolapsed)....Started Yoga becuase of free classes at a local Gym I was using at the time and have never looked back!
I still get back problems and have to be very careful when handling goods or bending, but running regularly now as well as Triathlons etc.
Don't go to classes anymore but try and preactise at home following recoreded TV classes (although not easy to follow when trying to perform the poses) but do try to do a Sun Salutation every a.m. & p.m. (more if poss') and sure this helps.
If my back does go, it now normally only lasts a day or so whereas before Yoga, it was sometimes months!!