I'm another one of those folks with lower back issues. Without going into too much detail, I'll just say that I have lost a lot of the curve that should be in the spine, and that I have a minor curvature in my upper back. I also have 3 chipped discs (in x-rays you can see a piece of the bone hanging suspended away from teh rest of the bone) in my lower back. I have been seeing a chiropractor for years, and we're able to keep my discomfort under relative control.
I do a series of lower back stretches before every single workout, and if my back is bothering me, I'll do those stretches during or after a workout, too. I can't tell you how much my lower back has improved since I started doing those stretches! I used to have all kinds of lower back pain, but not anymore. My chiropractor showed me how to do some of them, but I got most of them out of a book on stretching.
Perhaps if you're having lower back pain, doing these stretches will help. Again, ask your chiro to show you some or you can pick up any number of books on stretching for illustrated instructions on how to perform them.